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26780 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Linus Torvalds
|
f9a2394a23 |
Merge tag 'mm-hotfixes-stable-2026-08-06-18-44' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM fixes from Andrew Morton:
"17 hotfixes. 15 are cc:stable. 16 are for MM.
There's a patch series from Lorenzo "mm: fix UAF caused by race
between ptdump and vmap pgtable freeing" which addresses a quite old
bug in the ptdump code.
And another series also from Lorenzo which fixes a four year old bug
in the huge_zero_folio handling.
A series from SJ fixes a few possible divide-by-zero issues which
Sashiko sniffed out. And a series which fixes handling of the
commit_inputs parameters.
The remainder are singletons, please see their changelogs for details"
* tag 'mm-hotfixes-stable-2026-08-06-18-44' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}
mm/damon/ops-common: putback folios on invalid migrate nid
mm/huge_memory: initialise workingset state before folio split
mm/page_table_check: skip special zero mappings
mm/damon/lru_sort: skip damon_call() if ctx has not started
mm/damon/reclaim: skip damon_call() if ctx has not started
mm/damon/lru_sort: error out for >10000 active_mem_bp
samples/damon/mtier: error out for zero quota goal target values
mailmap: map old addresses to Danila Tikhonov
mm/huge_memory: separate out CONFIG_PERSISTENT_HUGE_ZERO_FOLIO logic
mm/huge_memory: fix huge_zero_pfn race
MAINTAINERS: update address for Brendan Jackman
mm/filemap: __filemap_add_folio() restore index before retrying
microblaze: restore the page alignment of swapper_pg_dir
arm64: remove redundant concurrent ptdump UAF mitigation
mm/ptdump: always stabilise against page table freeing using init_mm
mm/vmalloc: acquire init_mm lock on huge vmap to avoid ptdump UAF
|
||
|
Andy Lutomirski
|
478a1c3abe |
mm: fix incorrect flush address in direct page table reclaim
When zap_pte_range reclaims a page table, it does:
pte_free_tlb(tlb, pmd_pgtable(pmdval), addr);
and this is unconditionally wrong: if this code executes, addr *always*
points one past the end of the range covered by the table. The addr
parameter is used to flush the TLB (really the paging-structure-cache)
to drop references to the to-be-freed table, and any architecture that
cares about the parameter will flush the wrong address. (But they'll
still free the correct page).
I think it's worth contemplating why the kernel works at all.
If we hit the offending line of code, we will first clear the PMD entry
(line 1954, zap_empty_pte_table), then we will issue pending flushes if
force_flush is set (tlb_flush_mmu_tlbonly(tlb)), then we will skip the
retry on line 1979 (phew!), and then we will do the offending
pte_free_tlb call. *Or* we will clear the PMD entry immediately before
pte_free_tlb (line 1983, zap_pte_table_if_empty).
If we have any pending flushes (i.e. we actually zapped any last-level
entries) at the time we clear the PMD entry, then the flush really ought
to flush all references to the table (Linus certainly seems to think it
will on all architectures [0]).
The condition under which we have no accumulated flushes at the time of
the clear is very complex (the whole zap_pte_range function has absurdly
complex control flow). If we do hit the bad case, then we will end up
clearing the PMD entry after the last time the range is flushed, and any
CPU is free to cache a reference to the (empty) page table. If this
happens due to an ordinary read or write, it would segfault, so it would
be rare. But the cache could be speculatively filled as well. Then
we'll flush the wrong address and then free and possibly reuse the
table.
On x86, even flushing the wrong address works on non-KPTI Intel systems
because INVLPG flushes *all* paging-structure-caches, not just the ones
for the target address. But INVPCID does not, and flush_tlb_one_user
will use INVPCID if it's available. And then we're toast. AMD systems
are more susceptible: we set the EFER.TCE bit, which makes even INVLPG
only flush the target address.
I think this might fix an issue in ripgrep reported here:
https://github.com/BurntSushi/ripgrep/issues/3494
[0] https://lore.kernel.org/all/CA+55aFzBggoXtNXQeng5d_mRoDnaMBE5Y+URs+PHR67nUpMtaw@mail.gmail.com/T/#u
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Fixes:
|
||
|
SJ Park
|
1ec0e6b6f7 |
mm/damon: adjust isolated pages stat for DAMOS_MIGRATE_{HOT,COLD}
Callers of migrate_pages() should adjust NR_MIGRATED_{ANON,FILE} for
isolations and putback of the folios. That for migration succeeded folios
is done by migrate_pages(), in migrate_folio_done(). That for MR_DEMOTION
reason is an exception though.
DAMOS_MIGRATE_{HOT,COLD} call migrate_pages() but mistakenly not doing the
stat adjustment. As a result, use of DAMOS_MIGRATE_{HOT,COLD} could
corrupt the stat. It could confuse too_many_isolated(), make compaction
and reclaim to behave in unexpected ways. The stat corruption can be
reproduced and confirmed using DAMON user-space tool [1] on NUMA systems,
like below.
$ numactl --hardware
available: 2 nodes (0-1)
[...]
$ sudo ./damo start --damos_action migrate_hot 1
$ sudo cat /proc/sys/vm/stat_refresh
$ sudo dmesg
[...]
[ 80.215554] vmstat_refresh: nr_isolated_anon -5578
[ 80.216842] vmstat_refresh: nr_isolated_file -34400
This issue was discovered [2] by Sashiko.
Link: https://lore.kernel.org/20260728140404.94476-1-sj@kernel.org
Link: https://github.com/damonitor/damo [1]
Link: https://lore.kernel.org/20260726164356.87940-1-sj@kernel.org [2]
Fixes:
|
||
|
liyouhong
|
5deb65c34e |
mm/damon/ops-common: putback folios on invalid migrate nid
damon_pa_migrate() and damos_va_migrate() isolate folios into a local list
and then call damon_migrate_pages(). When target_nid is invalid
(including the scheme default NUMA_NO_NODE / -1), damon_migrate_pages()
returns early without putting the folios back to the LRU.
Callers then discard the list head while those folios remain isolated with
an extra reference taken by folio_isolate_lru(). The pages stay off the
LRU for as long as the mapping exists (anon active+inactive counts drop
while RSS does not), and the leftover references can pin the pages after
the mapping is gone.
Put the folios back on the invalid-nid path so ignored migration requests
still return them to the LRU.
Link: https://lore.kernel.org/20260726014815.1280757-1-dayou5941@163.com
Fixes:
|
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|
Matt Fleming
|
aca1f2d5de |
mm/huge_memory: initialise workingset state before folio split
xas_try_split() adds __GFP_ACCOUNT for page-cache xa_nodes, but
__folio_split() leaves the xa_state's xa_lru unset. That lets a live,
memcg-charged xa_node exist without being linked into the mapping's
shadow_nodes list_lru; when reclaim later walks the list_lru it trips
VM_WARN_ON(!css_is_dying()).
Use mapping_set_update() to install both the workingset update callback
and the shadow_nodes list_lru on the xa_state.
Link: https://lore.kernel.org/20260725101419.3938406-1-matt@readmodwrite.com
Fixes:
|
||
|
Zhiling Zou
|
8db4bab826 |
mm/page_table_check: skip special zero mappings
page_table_check_set() and page_table_check_clear() account mappings based
on PageAnon(). Shared zero-page PTEs and huge zero PMDs are special
mappings, but page_table_check can still account them as file-backed
pages.
An unprivileged process can populate enough zero mappings to overflow
file_map_count and hit the existing BUG_ON(). The PTE path can do this
with the shared zero page, and the PMD path can do the same with huge zero
mappings.
Skip special zero mappings in the user page-table accounting paths. Keep
the PTE-side pte_special() check, and identify huge zero PMDs from the
mapped folio instead of pmd_special(). That covers architectures where
pmd_special() is a no-op without adding huge_zero_pfn checks to the
generic counter helpers.
Link: https://lore.kernel.org/cover.1784717203.git.zhilinz@nebusec.ai
Link: https://lore.kernel.org/e94478e4fb7912fb7e8ebebed5ce85d00dc9a69d.1784717203.git.zhilinz@nebusec.ai
Fixes:
|
||
|
SJ Park
|
0f18683103 |
mm/damon/lru_sort: skip damon_call() if ctx has not started
DAMON_LRU_SORT calls damon_call() for commit_inputs parameter user input
if the DAMON context is initialized. The context could be initialized,
but not yet successfully started. In the case, damon_call() could
indefinitely hang. Read the comment on damon_call() for more detail. Fix
the problem by memorizing if the DAMON context has ever successfully
started, and skip damon_call() if it has not.
This issue can easily be reproduced by writing Y to the commit_inputs
parameter file on a system that DAMON_LRU_SORT has not turned on before.
Link: https://lore.kernel.org/20260803134646.16640-3-sj@kernel.org
Fixes:
|
||
|
SJ Park
|
b9b6bad94c |
mm/damon/reclaim: skip damon_call() if ctx has not started
Patch series "mm/damon/{reclaim,lru_sort}: fix commit_inputs infinite
hang".
Writing 'Y' to commit_inputs parameters of DAMON_RECLAIM and
DAMON_LRU_SORT before the modules were ever turned on causes infinite
hang. Fix those.
The issue was discovered [1] by Sashiko.
This patch (of 2):
DAMON_RECLAIM calls damon_call() for commit_inputs parameter user input if
the DAMON context is initialized. The context could be initialized, but
not yet successfully started. In the case, damon_call() could
indefinitely hang. Read the comment on damon_call() for more detail. Fix
the problem by memorizing if the DAMON context has ever successfully
started, and skip damon_call() if it has not.
This issue can easily be reproduced by writing Y to commit_inputs on a
system that DAMON_RECLAIM was not turned on before.
Link: https://lore.kernel.org/20260803134646.16640-1-sj@kernel.org
Link: https://lore.kernel.org/20260803134646.16640-2-sj@kernel.org
Link: https://lore.kernel.org/20260802173021.762-1-sj@kernel.org [1]
Fixes:
|
||
|
SJ Park
|
06befa61c4 |
mm/damon/lru_sort: error out for >10000 active_mem_bp
damos_quota_score() can trigger division by zero if the target value is
zero. DAMON_LRU_SORT lets users set the target value for the hot memory
scheme via active_mem_bp parameter. It avoids setting it as the target
value if the parameter value is zero. However, it also sets the cold
memory scheme with a target value that is calculated as '10000 -
active_mem_bp + 2'. Hence, if a user sets active_mem_bp 10002, the cold
memory scheme's quota goal target value can be zero. As a result,
division by zero can be triggered. Fix by returning an error when the
user tries to start DAMON with >10000 active_mem_bp parameter value.
It makes no sense to set active_mem_bp with 10002. It also requires
module parameters write permission to reproduce the issue. That said, the
consequence is quite bad.
One reliable way to reproduce the issue is like below:
# cd /sys/module/damon_lru_sort/parameters
# echo 1000 > wmarks_high
# echo 995 > wmarks_mid
# echo 0 > wmarks_low
# echo 10002 > active_mem_bp
# echo Y > enabled
# dmesg -w
[...]
[ 597.421247] Oops: divide error: 0000 [#1] SMP NOPTI
[ 597.428848] RIP: 0010:damos_quota_score+0x6f/0x480
This issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260803134034.15217-3-sj@kernel.org
Link: https://lore.kernel.org/20260801213028.5127-1-sj@kernel.org [1]
Fixes:
|
||
|
Lorenzo Stoakes (ARM)
|
98bd3af0bb |
mm/huge_memory: separate out CONFIG_PERSISTENT_HUGE_ZERO_FOLIO logic
Rather than mixing the refcounted and non-refcounted
CONFIG_PERSISTENT_HUGE_ZERO_FOLIO logic, separate the two out cleanly so
it is clear what happens when this configuration option is set and what
happens when it is not.
Introduce HUGE_ZERO_UNSET_PFN to abstract the ~0UL assignment, only
introduce the refcount, lock and shrinker if
!CONFIG_PERSISTENT_HUGE_ZERO_FOLIO, abstract initialisation and teardown,
abstract the huge zero folio allocation from refcounting.
Also change a BUG_ON() to WARN_ON_ONCE() while we're at it.
No functional change intended.
Link: https://lore.kernel.org/20260730-fix-refcounted-huge-zero-v2-2-c5d8a41b317f@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Fixes:
|
||
|
Lorenzo Stoakes (ARM)
|
33192a26cd |
mm/huge_memory: fix huge_zero_pfn race
Patch series "mm/huge_memory: fix huge_zero_pfn race", v2.
There is a subtle race in the reference-counted huge_zero_folio
implementation.
The fast path atomic logic fails to account for the fact that the shrinker
(which drops the final huge_zero_refcount pin) can overwrite huge_zero_pfn
with the ~0UL sentinel value in shrink_huge_zero_folio_scan() after a
racing get_huge_zero_folio() installed a valid value there.
This results in huge_zero_folio being correctly set but huge_zero_pfn
being set incorrectly and thus is_huge_zero_pfn() and consequently
is_huge_zero_pmd() will misidentify the huge zero folio as being an
ordinary THP folio.
This can result in the huge zero folio being split and otherwise treated
incorrectly.
The solution to this is very subtle as there is an atomic fast path, and
thus ordering in weakly ordered architectures has to be treated very
carefully.
The first commit fixes the issue by introducing a spinlock around
huge_zero_[pfn, folio, refcount] write, with careful consideration paid to
load/store ordering in the fast path. It is placed first and kept as
small as possible so that it can be backported on its own.
The second commit is a pure cleanup which reworks the
CONFIG_PERSISTENT_HUGE_ZERO_FOLIO logic to better separate the persistent
logic from the dynamically allocated one.
This patch (of 2):
If !CONFIG_PERSISTENT_HUGE_ZERO_FOLIO, the huge_zero_folio is refcounted
by huge_zero_refcount and returned by mm_get_huge_zero_folio().
When the caller is done with the huge zero page, its reference count is
decremented. Only a shrinker can set the reference count to zero.
A race can unfortunately occur between a shrinker decrementing the
reference count to zero and a concurrent page fault.
This is because shrink_huge_zero_folio_scan() might, if very unlucky, be
preempted between setting huge_zero_refcount to zero and writing an
invalid value.
During this time get_huge_zero_folio() could write to huge_zero_pfn before
shrink_huge_zero_folio_scan() resumes.
In this event the huge zero folio will be persistently misidentified
causing the THP code path to be entered inappropriately for the huge zero
folio:
CPU 0 CPU 1
=======================================|=================================
shrink_huge_zero_folio_scan() |
atomic_cmpxchg() sets refcount to 0 |
xchg() sets huge_zero_folio to NULL | get_huge_zero_folio()
| | atomic_inc_not_zero() -> zero
preempted for a long time | Allocate new huge zero folio
| | Write valid huge_zero_folio
v | Write valid huge_zero_pfn
Overwrite huge_zero_pfn with ~0UL <--- Invalid overwrite!
This results in is_huge_zero_pfn() and is_huge_zero_pmd() incorrectly
returning false for a huge zero page which could result in issues like the
huge zero folio being incorrectly split.
Note that the issue is with huge_zero_pfn not huge_zero_folio, as
get_huge_zero_folio() uses cmpxchg() gated on huge_zero_folio being NULL
with a retry loop and shrink_huge_zero_folio_scan() uses xchg() to set
huge_zero_folio.
Fix the issue by introducing a spinlock, huge_zero_lock, to prevent
concurrent write of huge_zero_folio, huge_zero_pfn and huge_zero_refcount.
There needs to be significant care taken here to ensure correctness:
The fast path in get_huge_zero_folio() uses atomic_inc_not_zero(), which
is outside of the critical section, and means huge zero allocation is
gated on zero huge_zero_refcount.
The fast path doesn't use huge_zero_lock, so the critical section is
irrelevant to it.
So invariants are required - huge_zero_refcount MUST:
* Only be set in the huge_zero_lock critical section to ensure
serialisation of huge_zero_pfn, huge_zero_folio and huge_zero_refcount
writes.
* Be set non-zero only AFTER huge_zero_[pfn, folio] are set to valid values
so installation of the huge zero folio on read page fault ensures
concurrent is_huge_zero_*() calls correctly identify the huge zero folio.
* Be set zero only BEFORE huge_zero_[pfn, folio] are set to NULL and ~0UL
respectively, and atomically.
Establish these by:
* Only setting huge_zero_refcount to zero or an absolute value in the
huge_zero_lock critical section in get_huge_zero_folio() and
shrink_huge_zero_folio_scan(), and always updating atomically there
and elsewhere.
* Using atomic_set_release(&huge_zero_refcount) in get_huge_zero_folio()
after huge_zero_[pfn, folio] are set. This is paired with
atomic_inc_not_zero() to ensure atomic_inc_not_zero() only observes a
non-zero value if huge_zero_[pfn, folio] are set.
* Using atomic_cmpxchg() in shrink_huge_zero_folio_scan() (as before) to
ensure that it is set zero only when equal to 1 and set atomically.
* atomic_cmpxchg() being fully ordered ensures this is done prior to
huge_zero_[folio, pfn] being set to NULL and ~0UL respectively.
Eliminate the retry loop in get_huge_zero_folio() as the atomic_cmpxchg()
in shrink_huge_zero_folio_scan() is now performed under the lock, and
replace with an equally locked atomic_inc() to set the reference count
should the caller be raced on huge zero folio installation.
folio_put() naturally implies a full memory barrier so its ordering is
maintained correctly.
The huge zero folio also cannot be released except when the shrinker does
so as it is non-LRU and non-rmappable.
Note that only the huge zero shrinker (via shrink_huge_zero_folio_scan())
can actually set huge_zero_refcount to zero, which is the count of mm's
which have at least one huge zero folio installed plus one shrinker pin.
Additionally convert a BUG_ON() to a VM_WARN_ON_ONCE().
Link: https://lore.kernel.org/20260730-fix-refcounted-huge-zero-v2-0-c5d8a41b317f@kernel.org
Link: https://lore.kernel.org/20260730-fix-refcounted-huge-zero-v2-1-c5d8a41b317f@kernel.org
Fixes:
|
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|
Hugh Dickins
|
86da3f7e1e |
mm/filemap: __filemap_add_folio() restore index before retrying
In __filemap_add_folio()'s split-a-conflict loop, xas_set_order() is
applied repeatedly: each application modifies xas.xa_index, rounding it
down according to the split_order attempted at that stage: and if all goes
as intended, it eventually (or immediately) converges on an
xas_try_split() to the required folio_order, with xas.xa_index now the
same as index: then xas_store() puts the new folio into the xarray there.
But if a new node was needed, and GFP_NOWAIT allocation did not get one,
the lock is dropped, xas_nomem() used to allocate, and sequence retried.
If (that part of) the xarray is unchanged when the lock is reacquired, no
problem. But what if the conflict was meanwhile resolved by another
thread (perhaps even doing the same thing, inserting a folio at that same
index)? Isn't there a danger of now putting our folio into the xarray at
an intermediate rounded-down index? With !folio_contains() bug to follow,
when CONFIG_DEBUG_VM=y is checking for that.
Fix this with an xas_set_order() to restore the original xas.xa_index at
the bottom of the loop, so the retry does a full re-evaluation after
reacquiring the lock, and cannot reach xas_store() with the wrong index.
Production was suffering from rare SIGILLs and SIGSEGVs, executable text
found a page away from where it belonged, !folio_contains() bug hit when
debug enabled: symptoms not seen since this patch went in.
Link: https://lore.kernel.org/562fbfa6-dd6d-0b6a-2461-ed2ff1173bc8@google.com
Fixes:
|
||
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Lorenzo Stoakes (ARM)
|
9d3277b2c0 |
arm64: remove redundant concurrent ptdump UAF mitigation
This partially reverts commit |
||
|
Lorenzo Stoakes (ARM)
|
27c32e5538 |
mm/ptdump: always stabilise against page table freeing using init_mm
Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit |
||
|
Lorenzo Stoakes (ARM)
|
26444eb714 |
mm/vmalloc: acquire init_mm lock on huge vmap to avoid ptdump UAF
Patch series "mm: fix UAF caused by race between ptdump and vmap pgtable freeing", v6. Kernel page table walkers fall into two broad categories - those ranges where no exclusion is required via walk_kernel_page_table_range_lockless() and those where exclusion is required via walk_kernel_page_table_range() or walk_page_range_debug(). The former category is used only by arm64 arch code operating on ranges it both wholly owns and does not concurrently write. The latter category consists of kernel page table walkers operating on ranges that are wholly owned (but which need exclusion against concurrent writers). The lock used for exclusion is the mmap lock, and for kernel ranges this is the mmap lock on init_mm. ptdump is a special case being both the only user of walk_page_range_debug(), and the only case in which it walks ranges it does not own. This presents a problem, as page tables may be freed under ptdump. And indeed there is a use-after-free bug in the kernel as a result, which this series addresses. vmap promotes page tables to huge leaf entries where possible, freeing the lower page table when it does. It does this with no meaningful locks held against concurrent ptdump walks. As a result, use-after-free can currently occur. This series addresses the issue by having the vmap huge promotion logic acquire the mmap read lock while both setting the huge page table entry and freeing the prior leaf page table. The ptdump code already acquires the mmap write lock, so by doing so we ensure that the ptdump walker only ever observes either the huge page table entry or the existing page table entry, and nothing is freed underneath it. A mitigation for this issue was already applied for arm64 in commit |
||
|
Link Lin
|
0b45f6927a |
mm/page_reporting: use system_freezable_wq to fix UAF during suspend
During PM freeze (e.g. S3 suspend or S4 hibernation), device drivers like
virtio_balloon reset their underlying virtio devices and delete their
virtqueues via vdev->config->del_vqs().
However, page reporting work (page_reporting_process) was scheduled on the
global system_wq. Because system_wq lacks the WQ_FREEZABLE flag, the PM
freezer skips it, leaving page_reporting_process active during suspend.
If pages are freed into the buddy allocator while suspending (for example,
when core MM invokes the balloon shrinker during S4 hibernation image
saving), page reporting triggers virtballoon_free_page_report() on deleted
virtqueues, resulting in a Use-After-Free / General Protection Fault:
[ 196.795226] general protection fault, probably for non-canonical address 0xaa1436fe70dae6df: 0000 [#1] SMP NOPTI
[ 196.825967] Workqueue: events page_reporting_process
[ 196.831038] RIP: 0010:virtqueue_add_split+0x233/0x4c0 [virtio_ring]
[ 196.927073] virtballoon_free_page_report+0x3a/0xe0 [virtio_balloon]
[ 196.946943] page_reporting_process+0x370/0x4f0
Fix this by switching page reporting work to system_freezable_wq. This
ensures that the PM freezer pauses page_reporting_process before device
drivers destroy their reporting virtqueues. Because the reporting worker
is frozen, memory reclamation/freeing (e.g. via shrinker execution) can
safely return pages to MM during freeze without triggering unfrozen
reporting work on deleted virtqueues.
This aligns with the driver's existing design. The comment in
virtballoon_freeze() states:
/*
* The workqueue is already frozen by the PM core before this
* function is called.
*/
Testing:
I have verified these fixes using Google’s virtualization infrastructure
by running continuous suspend/resume iterations (40+ cycles) while
churning memory using stress-ng (`stress-ng --vm 4 --vm-bytes 60%
--timeout 1`) to constantly create free pages for the buddy allocator. We
also set the `page_reporting_order` parameter to 0 to make the page
reporting worker highly sensitive, forcing it to pick up any 4K free
pages. This confirmed that the UAF crashes are no longer reproducible.
Link: https://lore.kernel.org/20260721005603.1710551-1-linkl@google.com
Fixes:
|
||
|
Richard Chang
|
dc37771a43 |
mm: vmscan: abort proactive reclaim early when freezing for suspend
Proactive reclaim (triggered via memory.reclaim or node sysfs) checks for pending signals in its outer loop in user_proactive_reclaim(). However, the inner reclaim loops—specifically scanning cgroups in shrink_many() and evicting/aging folios in try_to_shrink_lruvec()—can run for a long time before returning to the outer loop, especially on systems with many cgroups or large memory sizes. During system suspend, the PM freezer attempts to freeze all tasks by sending fake signals (setting TIF_SIGPENDING). Because the inner loops do not check for pending signals, the proactive reclaim task can remain stuck in kernel space for seconds, failing to enter the refrigerator in a timely manner. This leads to suspend failures due to freeze timeouts, a behavior observed on Android devices. This latency issue is specific to proactive reclaim because of its large, user-defined reclaim targets (could be gigabytes). Since commit |
||
|
Kiryl Shutsemau (Meta)
|
e923bd2105 |
mm/huge_memory: unlock i_mmap_rwsem before releasing after-split folios
__folio_split() keeps dereferencing the mapping after the split:
shmem_uncharge(mapping->host) and remap_page() while the folios are still
frozen/locked, and i_mmap_unlock_read(mapping) at the very end, after the
after-split folios have been unlocked and freed.
Nothing holds an inode reference across that. The split relies on @folio
-- which the beyond-EOF drop loop never removes, as it starts at
folio_next(folio) -- staying locked and in the page cache to hold off
eviction. But the unlock loop unlocks @folio before i_mmap_unlock_read()
runs. If the caller's @lock_at is a tail beyond EOF, as memory_failure()
passes when splitting a poisoned tail of a shmem THP that reaches past
i_size during truncation, it too is gone from the page cache; so once
@folio is unlocked no locked, in-cache folio pins the inode, and a
concurrent final iput() can evict and RCU-free it before
i_mmap_unlock_read() touches i_mmap_rwsem:
BUG: KASAN: slab-use-after-free in __up_read+0x634/0x790
i_mmap_unlock_read include/linux/fs.h:537 [inline]
__folio_split+0x732/0x1640 mm/huge_memory.c:4100
try_to_split_thp_page+0xab/0x390 mm/memory-failure.c:1675
memory_failure+0x1394/0x26e0 mm/memory-failure.c:2470
Freed by task 4601:
shmem_free_in_core_inode+0x54/0xb0 mm/shmem.c:5177
evict+0x57f/0xac0 fs/inode.c:870
Do every mapping dereference while @folio still pins the inode: drop
i_mmap_rwsem right after remap_page(), before the loop that unlocks and
frees the after-split folios, and clear @mapping so the exit path does not
unlock it again. shmem_uncharge() and remap_page() already run before
that point, so after this nothing past the unlock loop touches the inode
or the mapping.
This is now a rule the split depends on, alongside keeping @folio frozen
until the page cache is updated: no inode or mapping dereference once the
after-split folios start being unlocked.
Link: https://lore.kernel.org/20260716095424.471052-1-kirill@shutemov.name
Fixes:
|
||
|
Nico Pache
|
d09a8fd521 |
mm/migrate: exclude hugetlb folios from MTHP_STAT_NR_ANON accounting
__folio_migrate_mapping() increments MTHP_STAT_NR_ANON for the destination
folio when `folio_test_anon(folio) && folio_test_large(folio)` is true.
However, hugetlb folios satisfy both conditions despite having a
completely separate accounting system — they use hugetlb_add_anon_rmap()
which does not touch mTHP stats, and their free path also bypasses the
mTHP decrement in __free_pages_prepare().
This causes MTHP_STAT_NR_ANON to be incremented on each hugetlb migration
without a corresponding decrement, permanently inflating the nr_anon
counter.
Add a !folio_test_hugetlb() check to __folio_migrate_mapping() so that
only actual mTHP folios are counted.
Link: https://lore.kernel.org/20260717064502.1980173-3-npache@redhat.com
Fixes:
|
||
|
Nico Pache
|
4bd0c3515a |
mm: decrement MTHP_STAT_NR_ANON in free_zone_device_folio()
Patch series "mm: fix PMD level mTHP accounting bugs", v2.
While running selftests I noticed the PMD level per-mTHP stats (nr_anon)
remained elevated after each run. After further investigation I noticed
this accounting error occurs for both the migration.private_anon_htlb_test
and the HMM tests.
In the HMM case this is due to folio_add_new_anon_rmap() incrementing the
mTHP stats, but never containing a corresponding decrement in
free_zone_device_folio(). We solve this by making sure to decrement the
counter when freeing device memory.
In the migration case, we are incrementing this counter without first
checking whether this folio is a hugetlb folio, which relies on a separate
accounting system. We solve this by adding the proper hugetlb check
before incrementing this counter.
With these changes in place, the two tests no longer cause elevated PMD
level accounting issues.
This patch (of 2):
When a zone device folio is mapped as anonymous, folio_add_new_anon_rmap()
increments MTHP_STAT_NR_ANON. The corresponding decrement lives in
__free_pages_prepare() in page_alloc.c, but zone device folios are freed
via free_zone_device_folio() which never calls __free_pages_prepare().
This causes nr_anon to remain permanently elevated after zone device
folios are freed.
Add the missing mod_mthp_stat() decrement to free_zone_device_folio() so
that the counter is properly balanced.
Link: https://lore.kernel.org/20260717064502.1980173-1-npache@redhat.com
Link: https://lore.kernel.org/20260717064502.1980173-2-npache@redhat.com
Fixes:
|
||
|
Breno Leitao
|
1833ce36b3 |
mm: memcg: initialize *locked in memcg1_oom_prepare() stub
mem_cgroup_oom() passes an uninitialized "locked" to memcg1_oom_prepare()
and reads it back in memcg1_oom_finish():
bool locked, ret;
...
if (!memcg1_oom_prepare(memcg, &locked))
return false;
ret = mem_cgroup_out_of_memory(memcg, mask, order);
memcg1_oom_finish(memcg, locked);
This relies on memcg1_oom_prepare() setting *locked whenever it returns
true. The CONFIG_MEMCG_V1=y version does, but the stub used when
CONFIG_MEMCG_V1=n returns true without touching *locked, so
memcg1_oom_finish() consumes an uninitialized value. On a memcg OOM this
is reported by UBSAN:
UBSAN: invalid-load in mm/memcontrol.c:1932:27
load of value 0 is not a valid value for type 'bool' (aka '_Bool')
Initialize *locked to false in the stub; with cgroup v1 compiled out there
is no OOM lock to take.
Link: https://lore.kernel.org/20260716-memcg-oom-uninit-locked-v2-1-63631d878eb4@debian.org
Fixes:
|
||
|
Linus Torvalds
|
62cc902415 |
Merge tag 'mm-hotfixes-stable-2026-07-27-14-18' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton: "13 hotfixes. All are cc:stable. 11 are for MM. All are singletons - please see the changelogs for details" * tag 'mm-hotfixes-stable-2026-07-27-14-18' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: fs/proc/task_mmu: fix PAGEMAP_SCAN written state for PMD holes mm/hugetlb: fix list corruption in allocate_file_region_entries() mm: mglru: fix stale batch updates after memcg reparenting selftest: fix headers in fclog.c ocfs2: fix boundary check in ocfs2_check_dir_entry() to use buffer offset mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk() mm/util: don't read __page_2 for order-1 folios in snapshot_page() mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork() mm: migrate_device: fix pte_pfn/pte_dirty called on non-present PTE fs/proc/task_mmu: fix PAGEMAP_SCAN written state for unpopulated ptes userfaultfd: wait on source PMD during UFFDIO_MOVE lib: test_hmm: use device devt for coherent device range selection mm/vmstat: fold stranded per-cpu node stats when a node comes online |
||
|
Linus Torvalds
|
4235cb24ec |
Merge tag 'vfs-7.2-rc5.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs fixes from Christian Brauner:
- vfs: Preserve the ACL_DONT_CACHE state in forget_cached_acl().
ACL_DONT_CACHE is meant to be a permanent opt-out from ACL caching
which FUSE relies on for servers that don't negotiate FUSE_POSIX_ACL.
The helper replaced it with ACL_NOT_CACHED, silently re-enabling the
cache, and as fuse doesn't invalidate the cache for such servers a
properly timed get_acl() returned stale ACLs. Comes with a fuse
selftest reproducing this.
- pidfs:
- Preserve PIDFD_THREAD when a thread pidfd is reopened via
open_by_handle_at(). PIDFD_THREAD shares the O_EXCL bit which
do_dentry_open() strips after the flags have been validated, so
the reopened pidfd silently became a process pidfd. Comes with a
selftest.
- Add a pidfs_dentry_open() helper so the regular pidfd allocation
path and the file handle path share the code that forces O_RDWR
and reapplies the pidfd flags that do_dentry_open() strips.
- Handle FS_IOC32_GETVERSION in the compat ioctl path.
- Make pidfs_ino_lock static.
- iomap:
- Fix the block range calculation in ifs_clear_range_dirty() so a
partial clear doesn't drop the dirty state of blocks the range
only partially covers.
- Support invalidating partial folios so a partial truncate or hole
punch with blocksize < foliosize doesn't leave stale dirty bits
behind.
- Only set did_zero when iomap_zero_iter() actually zeroed
something.
- Guard ifs_set_range_dirty() and ifs_set_range_uptodate() against
zero-length ranges where the unsigned last-block calculation
underflows and bitmap_set() writes far beyond the ifs->state
allocation.
- Don't merge ioends with different io_private values as the merge
could leak or corrupt the private data of the individual ioends.
- exec:
- Raise bprm->have_execfd only once the binfmt_misc interpreter has
actually been opened. The flag was set as soon as a matching 'O'
or 'C' entry was found. If the interpreter open failed with
ENOEXEC the exec fell through to the next binary format with
have_execfd raised but no executable staged and begin_new_exec()
NULL derefed past the point of no return.
- Fix an unsigned loop counter wrap in transfer_args_to_stack() on
nommu. An overlong argument or environment string pushes bprm->p
below PAGE_SIZE, the stop index becomes zero, and the loop never
terminates, wrapping its counter and copying garbage from in
front of the page array into the new process stack.
- Make binfmt_elf_fdpic only honour the first PT_INTERP like
binfmt_elf does. Each additional PT_INTERP overwrote the previous
interpreter, leaking the name allocation and the interpreter file
reference together with the write denial open_exec() took,
leaving the file unwritable for as long as the system runs.
- overlayfs:
- Compare the full escaped xattr prefix including the trailing dot.
An xattr like "trusted.overlay.overlayfoo" was misclassified as
an escaped overlay xattr.
- Check read access to the copy_file_range() source with the
source's mounter credentials.
- super: Thawing a filesystem whose block device was frozen with
bdev_freeze() deadlocked. Dropping the last block layer freeze
reference from under s_umount ends up in fs_bdev_thaw() which
reacquires s_umount on the same task. Pin the superblock with an
active reference instead and call bdev_thaw() without holding
s_umount.
- procfs: Return EACCES instead of success when the ptrace access check
for namespace links fails.
- afs: Use afs_dir_get_block() rather than afs_dir_find_block() for
block 0 in afs_edit_dir_remove(), matching afs_edit_dir_add().
- Push the memcg gating of ->nr_cached_objects() down into the btrfs
and shmem callbacks instead of skipping every callback during
non-root memcg reclaim. The blanket check short-circuited XFS whose
inode reclaim hook is intentionally driven from per-memcg contexts to
free memcg-charged slab.
- eventpoll: Pin files while checking reverse paths.
Since struct file became SLAB_TYPESAFE_BY_RCU a concurrent close
could free and recycle the file under the check which then took and
dropped the f_lock of whatever live file now occupies that slot.
* tag 'vfs-7.2-rc5.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
super: fix emergency thaw deadlock on frozen block devices
pidfs: make pidfs_ino_lock static
eventpoll: pin files while checking reverse paths
fs: push nr_cached_objects memcg gating into individual filesystems
afs: Fix afs_edit_dir_remove() to get, not find, block 0
iomap: prevent ioend merge when io_private differs
iomap: add comments for ifs_clear/set_range_dirty()
iomap: fix out-of-bounds bitmap_set() with zero-length range
iomap: fix incorrect did_zero setting in iomap_zero_iter()
iomap: support invalidating partial folios
iomap: correct the range of a partial dirty clear
fs/super: fix emergency thaw double-unlock of s_umount
pidfs: handle FS_IOC32_GETVERSION in compat ioctl
ovl: check access to copy_file_range source with src mounter creds
proc: Fix broken error paths for namespace links
pidfs: add pidfs_dentry_open() helper
selftests/pidfd: check PIDFD_THREAD survives open_by_handle_at()
pidfs: preserve thread pidfds reopened by file handle
ovl: fix trusted xattr escape prefix matching
selftests/fuse: add ACL_DONT_CACHE regression test
...
|
||
|
Linus Torvalds
|
86ba24c41a |
Merge tag 'slab-for-7.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab
Pull slab fixes from Vlastimil Babka: - Prevent unbounded recursion in free path with memory allocation profiling, which has caused a stack overflow on a Meta production host due to a 125-deep __free_slab<->kfree recursion (Harry Yoo) - Fix type-based partitioning confusing sparse which does not know __builtin_infer_alloc_token() (Marco Elver) - Fix a potential memory leak in bulk freeing path on NUMA machines (Shengming Hu) * tag 'slab-for-7.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: slab: silence sparse warning with type-based partitioning mm/slab: prevent unbounded recursion in free path with new kmalloc type lib/alloc_tag: introduce mem_alloc_profiling_permanently_disabled() mm/slab: decouple SLAB_NO_SHEAVES from SLAB_NO_OBJ_EXT mm/slab: fix a memory leak due to bootstrapping sheaves twice mm/slub: fix lost local objects when bulk remote free batch fills |
||
|
Usama Arif
|
0ef8faff49 |
fs: push nr_cached_objects memcg gating into individual filesystems
Commit |
||
|
Xiangfeng Cai
|
dd9623f58e |
mm/hugetlb: fix list corruption in allocate_file_region_entries()
allocate_file_region_entries() tops up resv->region_cache with freshly
allocated file_region descriptors. The allocation uses GFP_KERNEL, so
resv->lock is dropped around it: the new entries are gathered on a
stack-local list head, allocated_regions, and spliced into
resv->region_cache once the lock is re-acquired.
The splice used list_splice(), which moves the entries but does not
re-initialize the source head, so allocated_regions is left pointing at an
entry that now lives on resv->region_cache. The top-up runs in a while
loop that re-checks the cache deficit after re-acquiring the lock. For a
shared mapping the resv_map is shared by every mapper of the hugetlbfs
inode, so a concurrent region_chg()/region_add()/region_del() on the same
resv_map can consume cache entries during the unlocked window and force a
second iteration. That iteration calls list_add() on the stale head and
corrupts the list; with CONFIG_DEBUG_LIST the __list_add_valid() check
trips:
list_add corruption. next->prev should be prev (ffffc900011ff7f8),
but was ffff88814c281460. (next=ffff88814c545640).
kernel BUG at lib/list_debug.c:31!
allocate_file_region_entries+0x191/0x420
region_chg+0x267/0x300
hugetlb_reserve_pages+0x387/0xc80
hugetlbfs_file_mmap+0x2ce/0x3f0
mmap_region+0x1348/0x1a80
do_mmap+0x85e/0xb90
vm_mmap_pgoff+0x18c/0x330
ksys_mmap_pgoff+0x2a1/0x3e0
do_syscall_64+0xd7/0x420
Without CONFIG_DEBUG_LIST the bad list_add() silently links a kernel-stack
address into resv->region_cache, leading to later use-after-free.
This was observed as a real host panic on a dense KVM host where a QEMU
guest-RAM hugetlbfs file was mapped MAP_SHARED by both QEMU and a separate
SPDK/DPDK vhost-user target, generating concurrent region_* traffic on one
shared resv_map.
Use list_splice_init() so the source head is re-initialized empty after
each splice, making the retry loop safe.
Link: https://lore.kernel.org/20260713171456.300518-2-caixiangfeng@bytedance.com
Fixes:
|
||
|
Qi Zheng
|
de4660898b |
mm: mglru: fix stale batch updates after memcg reparenting
The mglru page table walker batches per-generation size deltas in
walk->nr_pages while walking page tables without holding the lruvec lock.
The reset_batch_size() later folds those deltas into walk->lruvec under
the lruvec lock.
The page table walker can run concurrently with the memcg reparenting path
as follows:
CPU0 CPU1
==== ====
walk_mm
--> walk_page_range
--> update_batch_size
--> walk->nr_pages += delta
mem_cgroup_css_offline
--> memcg_reparent_objcgs
--> lock lruvec
lru_gen_reparent_memcg
--> reparent child folios to parent
unlock lruvec
lock lruvec
reset_batch_size
--> child lrugen->nr_pages += delta
This will trigger the following warning in lru_gen_exit_memcg():
VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
sizeof(lruvec->lrugen.nr_pages)));
And the user-visible impact of underestimated nr_pages in MGLRU was
premature OOMs because MGLRU does not try to reclaim memory when nr_pages
reaches zero, but there are still more pages.
To fix it, make reset_batch_size() check CSS_DYING under RCU before
flushing the pending batch. A non-dying memcg keeps the original lruvec
stable against RCU-delayed offlining; a dying memcg redirects the deltas
to the first non-dying ancestor.
Link: https://lore.kernel.org/20260710154318.75388-1-qi.zheng@linux.dev
Fixes:
|
||
|
Zi Yan
|
89b1b79c30 |
mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk()
In pcpu_create_chunk(), nr_pages is the total contiguous backing allocation, i.e., nr_units * pcpu_unit_pages, but pcpu_chunk_populated() uses it to set chunk->populated, whose size is pcpu_unit_pages, bitmap. Since bit N in chunk->populated means page offset N inside every unit is backed. When nr_units > 1, the function writes beyond chunk->populated. Fix it by using chunk->nr_pages. It also fixes the global pcpu_nr_empty_pop_pages accounting, since pcpu_balance_free() only iterates up to chunk->nr_pages. Commit |
||
|
Aboorva Devarajan
|
7441d6348c |
mm/util: don't read __page_2 for order-1 folios in snapshot_page()
snapshot_page() currently reads __page_2 after checking nr_pages > 1, but
it should only do so when nr_pages > 2.
If an order-1 folio is allocated at the end of a vmemmap section,
__page_2 will not exist and reading it will cause a fault.
During DLPAR memory remove on a 22 TB ppc64le LPAR, snapshot_page() oopsed
on the page isolation path while reading an order-1 folio's __page_2 from
an adjacent absent section (unmapped vmemmap).
Fix this to avoid reading memmap that doesn't exist (e.g., a vmemmap
hole).
Link: https://lore.kernel.org/20260708201954.686111-1-aboorvad@linux.ibm.com
Fixes:
|
||
|
Kiryl Shutsemau (Meta)
|
83abe2fd5b |
mm/hugetlb: fix swap entry corruption when clearing uffd-wp at fork()
copy_hugetlb_page_range() clears the uffd-wp bit of migration and hwpoison
entries with huge_pte_clear_uffd_wp(), which operates on the present-PTE
bit position. Swap entries keep the uffd-wp state elsewhere -- the
migration branch reads and sets it with pte_swp_uffd_wp() and
pte_swp_mkuffd_wp() -- and the present-PTE position falls into the swap
payload. On x86-64 it lands in the inverted swap offset, where a
naturally-aligned hugetlb PFN always has the affected bit set, so the
clear advances the encoded PFN by two pages.
No userfaultfd needs to be involved: the clear is guarded only by the
child VMA not being uffd-wp registered, so a plain fork() with an
in-flight hugetlb migration entry (or a poisoned hugetlb page) corrupts
the entry copied into the child. Instrumenting the clear and forking
after MADV_HWPOISON on a 2MB anon hugetlb page shows:
offset before=120e00
offset after =120e02
The fallout is mostly latent: rmap walks match migration entries by folio
range and remove_migration_pte() rebuilds the PTE from the folio, so a
within-folio PFN skew heals once migration completes. But any path that
re-encodes the corrupted offset -- e.g. hugetlb_change_protection()
rewriting a writable migration entry via
make_readable_migration_entry(swp_offset(entry)) -- propagates it.
Migration entries legitimately carry uffd-wp, so clear it with
pte_swp_clear_uffd_wp(), matching copy_nonpresent_pte() and
move_huge_pte().
A hwpoison entry, on the other hand, never carries the uffd-wp bit: it is
installed fresh by make_hwpoison_entry() (try_to_unmap_one() does not
preserve uffd-wp on the hwpoison path) and hugetlb_change_protection()
leaves hwpoison entries untouched. There was nothing to clear there, only
the corruption, so drop the clear entirely.
Link: https://lore.kernel.org/20260708090110.136162-1-kirill@shutemov.name
Fixes:
|
||
|
Kefeng Wang
|
63867c82d0 |
mm: migrate_device: fix pte_pfn/pte_dirty called on non-present PTE
pte_pfn() and pte_dirty() have undefined behaviour when called on a non-present PTE. In migrate_vma_collect_pmd(), these functions may be invoked on non-present entries (e.g., device-private entries), leading to potential crashes from pte_pfn() or incorrect dirty folio accounting from pte_dirty(). Fix both by guarding with pte_present() checks. Link: https://lore.kernel.org/20260708003955.4024340-1-wangkefeng.wang@huawei.com Link: https://lore.kernel.org/20260706111958.3649651-1-wangkefeng.wang@huawei.com Fixes: |
||
|
Usama Arif
|
4165b7d1c4 |
userfaultfd: wait on source PMD during UFFDIO_MOVE
move_pages_huge_pmd() snapshots src_pmdval under src_ptl, drops the lock,
and, for migration entries, waits with pmd_migration_entry_wait().
Passing &src_pmdval is wrong. pmd_migration_entry_wait() must lock and
re-read the real page-table PMD; on split-PMD-lock kernels, a stack
address also resolves to the wrong lock. softleaf_entry_wait_on_locked()
then waits without a folio reference, which is safe only while serialized
against migration-entry removal by the real PT lock.
Pass src_pmd, matching __handle_mm_fault() and hmm_vma_walk_pmd().
Link: https://lore.kernel.org/20260705131231.1499198-1-usama.arif@linux.dev
Fixes:
|
||
|
Gregory Price
|
ea3034b2b0 |
mm/vmstat: fold stranded per-cpu node stats when a node comes online
A per-node vmstat counter is pgdat->vm_stat[] plus per-cpu deltas. A
balanced counter can sit split as global=+N / per-cpu=-N.
The folds reconciling the split only walk online nodes, so when
try_offline_node() marks a node offline the per-cpu deltas are stranded.
A subsequent online resets the per-cpu area but not pgdat->vm_stat[],
orphaning the +N permanently. All NR_VM_NODE_STAT_ITEMS are affected.
The existing code zeroes the per-cpu counters and causes a permanent skew.
Fold the stranded deltas instead, before the node rejoins the online set.
The node is not online yet and the hotplug lock is held, so the remote
access to per-cpu values is safe.
Discovered when node compaction hung for a nearly empty node, as the math
to determine throttling broke. Reproduced by repeated memory
hotplug/unplug cycles on a node under pressure: NR_ISOLATED_ANON ratchets
up and never returns to zero.
Link: https://lore.kernel.org/20260627202243.758289-1-gourry@gourry.net
Fixes:
|
||
|
Linus Torvalds
|
b95f03f04d |
Merge tag 'mm-hotfixes-stable-2026-07-20-11-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton: "12 hotfixes. 8 are cc:stable and the remainder address post-7.1 issues or aren't considered appropriate for backporting. 10 are for MM. All are singletons - please see the relevant changelogs for details" * tag 'mm-hotfixes-stable-2026-07-20-11-37' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: mm/memory-failure: trace: change memory_failure_event to ras subsystem mm: page_reporting: allow driver to set batch capacity mm/kmemleak: fix checksum computation for per-cpu objects mm/damon/core: disallow overlapping input ranges for damon_set_regions() MAINTAINERS: add Usama as a THP reviewer fat: avoid stack overflow warning mm/damon/core: validate ranges in damon_set_regions() m68k: avoid -Wunused-but-set-parameter in clear_user_page() mm/huge_memory: set PG_has_hwpoisoned only after new folio head is established mm/page_vma_mapped: fix device-private PMD handling MAINTAINERS: s/SeongJae/SJ/ userfaultfd: prevent registration of special VMAs |
||
|
Harry Yoo (Oracle)
|
d9e6a76239 |
mm/slab: prevent unbounded recursion in free path with new kmalloc type
Commit |
||
|
Harry Yoo (Oracle)
|
982e31382d |
mm/slab: decouple SLAB_NO_SHEAVES from SLAB_NO_OBJ_EXT
Bootstrap caches are created with SLAB_NO_OBJ_EXT to disallow sheaves and obj_exts. To allow disabling obj_exts while allowing sheaves, decouple SLAB_NO_SHEAVES from SLAB_NO_OBJ_EXT. Bootstrap caches now have both SLAB_NO_SHEAVES and SLAB_NO_OBJ_EXT. No functional change intended. Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org> Signed-off-by: Harry Yoo (Oracle) <harry@kernel.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Link: https://patch.msgid.link/20260713-kmalloc-no-objext-v3-2-47c7bd138de7@kernel.org Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org> |
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Harry Yoo (Oracle)
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1dba91a049 |
mm/slab: fix a memory leak due to bootstrapping sheaves twice
When kmalloc caches are aliased, multiple cache pointers reference
the same kmem_cache. As a result, iterating over kmalloc indices and
bootstrapping sheaves can bootstrap the same cache more than once and
leak memory.
Currently, this could happen when the architecture specifies
minimum alignment for slab caches that is larger than
ARCH_KMALLOC_MINALIGN.
Bootstrap sheaves only when the cache does not have them already.
Add a warning when bootstrap_cache_sheaves() is called for a cache
that already has sheaves enabled.
Fixes:
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Vivian Wang
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4edd70ee6a |
mm/sparse-vmemmap: flush_cache_vmap() after hotplugging vmemmap
section_activate() does not flush TLB after populating new vmemmap pages. On most architectures, this is okay. However it is a problem on RISC-V since there the TLB caching non-present entries is permitted, which causes spurious faults on some hardwares. This seems to be most easily reproduced with DEBUG_VM=y and PAGE_POISONING=y, which causes these newly mapped struct pages to be poisoned i.e. written to immediately after mapping. Extend the RISC-V flush_cache_vmap() to also handle the vmemmap range, and call it after hotplugging vmemmap, which gets the possible spurious fault handled in the exception handler. At least for now, the only other architecture with both SPARSEMEM_VMEMMAP and flush_cache_vmap() is PowerPC, which has a similar problem with newly valid PTEs. But there flush_cache_vmap() is just a ptesync. So it should be safe to do this for generic code while having minimal performance impact. Suggested-by: Muchun Song <muchun.song@linux.dev> Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn> Reviewed-by: Muchun Song <muchun.song@linux.dev> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Link: https://patch.msgid.link/20260713-mark-after-vmemmap-populate-v6-2-b945ceba29d4@iscas.ac.cn Signed-off-by: Paul Walmsley <pjw@kernel.org> |
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Michael S. Tsirkin
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47c81dadb7 |
mm: page_reporting: allow driver to set batch capacity
At the moment, if a virtio balloon device has a page reporting vq but its
size is < PAGE_REPORTING_CAPACITY (32), the balloon driver fails probe.
But, there's no way for host to know this value, so it can easily create a
smaller vq and suddenly adding the reporting capability to the device
makes all of the driver fail. Not pretty.
Add a capacity field to page_reporting_dev_info so drivers can control the
maximum number of pages per report batch.
In virtio-balloon, set the capacity to the reporting virtqueue size,
letting page_reporting adapt to whatever the device provides.
Capacity need not be a power of two. Code previously called out division
by PAGE_REPORTING_CAPACITY as cheap since it was a power of 2, but no
performance difference was observed with non-power-of-2 values.
If capacity is 0 or exceeds PAGE_REPORTING_CAPACITY, it defaults to
PAGE_REPORTING_CAPACITY. The 0 check and the clamping is done in
page_reporting_register(), before the reporting work is scheduled, so we
never get division by 0.
Link: https://lore.kernel.org/444c24cf39f3f3620fc90ef4695bd6b0979f4c4b.1783232420.git.mst@redhat.com
Fixes:
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Breno Leitao
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79c37ae373 |
mm/kmemleak: fix checksum computation for per-cpu objects
The per-cpu object checksum folds each CPU's CRC together with XOR and
seeds every CRC with 0. Both choices make update_checksum() miss content
changes:
- XOR is self-cancelling, so equal contents on two CPUs cancel out and
simultaneous identical changes leave the checksum unchanged.
- crc32(0, ...) over all-zero content is 0, so a freshly allocated,
zeroed per-cpu area checksums to 0, matching the initial value, and
the object is never seen to change.
See discussions at [0].
When update_checksum() wrongly reports an actively modified object as
unchanged, kmemleak stops greying it for an extra scan and can report a
live per-cpu object as a leak.
Fold the per-cpu CRC as a single rolling checksum across all CPUs and
initialise the object checksum to ~0 so the first computed value always
registers as a change, even for content that hashes to 0.
reset_checksum() is seeded the same way.
Link: https://lore.kernel.org/all/akfYImSNDh3OjIfR@gmail.com [0]
Link: https://lore.kernel.org/20260703-kmemleak_checksum-v1-1-5e0ab7d6966f@debian.org
Fixes:
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SJ Park
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954157679e |
mm/damon/core: disallow overlapping input ranges for damon_set_regions()
damon_set_regions() assumes the input ranges are sorted by the address and don't overlap each other. Hence the assumption was initially to be explicitly validated. But commit |
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SJ Park
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1292c0ecb1 |
mm/damon/core: validate ranges in damon_set_regions()
DAMON core logic assumes zero length regions don't exist. However, a few
DAMON API callers including DAMON_SYSFS, DAMON_RECLAIM and DAMON_LRU_SORT
allow users to set empty monitoring target regions. This could result in
WARN_ONCE() on CONFIG_DAMON_DEBUG_SANITY enabled kernel, and
divide-by-zero from damon_merge_two_regions().
For example, the WANR_ONCE() can be triggered like below.
# grep DAMON_DEBUG_SANITY /boot/config-$(uname -r)
# CONFIG_DAMON_DEBUG_SANITY=y
# damo start
# cd /sys/kernel/mm/damon/admin/kdamonds/0
# echo 0 > contexts/0/targets/0/regions/0/start
# echo 0 > contexts/0/targets/0/regions/0/end
# echo commit > state
# dmesg
[....]
[ 73.705780] ------------[ cut here ]------------
[ 73.707552] start 0 >= end 0
[ 73.708452] WARNING: mm/damon/core.c:359 at damon_new_region+0x6e/0x80, CPU#1: kdamond.0/758
[...]
All DAMON API callers eventually use damon_set_regions() to setup the
regions. Add the validation logic in the function.
Link: https://lore.kernel.org/20260630035221.146458-1-sj@kernel.org
Fixes:
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Rik van Riel
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e1cd30eceb |
mm/huge_memory: set PG_has_hwpoisoned only after new folio head is established
__split_folio_to_order() copies the hwpoison state onto each new sub-folio while splitting a folio to a non-zero order. It does so via if (handle_hwpoison && page_range_has_hwpoisoned(new_head, new_nr_pages)) folio_set_has_hwpoisoned(new_folio); *before* clear_compound_head(new_head)/prep_compound_page(new_head, ...) turns @new_head from a tail page into a proper folio head. PG_has_hwpoisoned is a FOLIO_SECOND_PAGE flag, so folio_set_has_hwpoisoned() resolves to folio_flags(folio, 1). With the new compound_info-based page-flags layout, folio_flags() asserts the page is not a tail: VM_BUG_ON_PGFLAGS(page->compound_info & 1, page); VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags.f), page); At the current call site @new_head still has the tail marker (compound_info bit 0 set, PG_head clear), so on CONFIG_DEBUG_VM kernels this hits: kernel BUG at include/linux/page-flags.h:354 folio_flags+0x82 folio_set_has_hwpoisoned __split_folio_to_order __split_unmapped_folio __folio_split truncate_inode_partial_folio (shmem hole-punch / MADV_REMOVE) Reproduced by syzkaller: hwpoison-inject a few subpages of a large shmem folio, then MADV_REMOVE (fallocate punch hole) on the same range, which splits the partial folio to a non-zero order. memory_failure() tries to split the poisoned folio to order 0 first, but that split is best-effort; when it fails the folio is left large with PG_has_hwpoisoned set, the case |
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Wei Yang
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f84ca9b188 |
mm/page_vma_mapped: fix device-private PMD handling
Commit |
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SJ Park
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14afcf67dc |
MAINTAINERS: s/SeongJae/SJ/
My legal and preferred first names are SeongJae and SJ, respectively. I was using the legal name for commits and tags, while using the preferred name for conversations. It sometimes confuses people including myself. Consistently use the preferred name. Together remove copyright notes on files. Those are only confusing for people who are not familiar with the law. Meanwhile, we can infer the information in a better way from git logs and public information. Link: https://lore.kernel.org/20260630013820.143366-1-sj@kernel.org Signed-off-by: SJ Park <sj@kernel.org> Acked-by: Lorenzo Stoakes <ljs@kernel.org> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Cc: Liam R. Howlett <liam@infradead.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Mike Rapoport (Microsoft)
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3c58f641e8 |
userfaultfd: prevent registration of special VMAs
Vova Tokarev says:
userfaultfd allows registration on shadow stack VMAs. With userfaultfd
access, you can register on the shadow stack, discard a page ... and
inject a page with chosen return addresses via UFFDIO_COPY.
Update vma_can_userfault() to reject VM_SHADOW_STACK.
While on it, also reject VM_SPECIAL so that if a driver would implement
vm_uffd_ops, it wouldn't be possible to register special VMAs with
userfaultfd.
Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude
hugetlb VMAs from the check for VM_SPECIAL.
Link: https://lore.kernel.org/20260618095017.2553004-1-rppt@kernel.org
Fixes:
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Shengming Hu
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af9ea231c0 |
mm/slub: fix lost local objects when bulk remote free batch fills
In free_to_pcs_bulk(), when remote_objects[] fills to PCS_BATCH_MAX,
the code jumps to flush_remote to free the batch. If all remote entries
have already been compacted out of p[] via tail swaps while local objects
remain, the flush_remote path returns early since `i < size` no longer
holds. The leftover local objects are then neither cached in the sheaf
nor returned to the slab freelist, causing a memory leak.
For illustration:
size = 64, local objects at p[0..31], remote objects at p[32..63]
After scanning all remotes: i = 32, size = 32
p[0..31] local objects are dropped.
Harry pointed out that, although the logic contains a real leak, it does
not appear to be triggerable with the current in-tree users. To hit this
path, at least PCS_BATCH_MAX objects, currently hardcoded to 32, need to
be collected in remote_objects[]. Looking at current kmem_cache_free_bulk()
users:
* maple_node has sheaf_capacity = 32
* skbuff_head_cache has sheaf_capacity = 28
* panthor and msm drivers have sheaf_capacity = 4
The sheaf capacity is, at least for now, derived purely from the object
size, with the user-requested capacity used as a minimum. Therefore, among
the current users, only maple_node has a sheaf_capacity large enough to
reach PCS_BATCH_MAX.
However, for the bug to trigger in maple_node, all objects in the sheaf
would have to be from remote nodes. In that case, there would be no local
objects left to leak. So this issue was found by code review rather than
from a runtime report, and it does not seem to be triggerable by current
users.
Still, the bug could become reachable with future users, a different sheaf
capacity, or a change to PCS_BATCH_MAX. Fix the logic by freeing a full
remote batch in place during the scan and then continuing to process the
compacted array. This keeps all local objects on the normal fast path,
while the tail path only handles any leftover partial remote batch. The
redundant next_remote_batch jump label is removed as well.
Fixes:
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Pedro Falcato
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e187bc02f8 |
mm: do file ownership checks with the proper mount idmap
Ever since idmapped mounts were introduced, inode ownership checks (for
side-channel protection) in mincore() and madvise(MADV_PAGEOUT) were done
against the nop_mnt_idmap, which completely ignores the file's mount's
idmap. This results in odd edgecases like:
1) mount/bind-mount with an idmap userA:userB:1
2) userB runs an owner_or_capable() check on file that is owned by userA
on-disk/in-memory, but owned by userB after idmap translation
3) owner_or_capable() mysteriously fails as the correct idmap wasn't supplied
In the case of mincore/madvise MADV_PAGEOUT, this is usually benign,
because file_permission(file, MAY_WRITE) will probably succeed, as it uses
the proper idmap internally, but it does not need to be the case on e.g a
0444 file where even the owner itself doesn't have permissions to write to
it.
Since this is clearly not trivial to get right, introduce a
file_owner_or_capable() that can carry the correct semantics, and switch
the various users in mm to it.
The issue was found by manual code inspection & an off-list discussion
with Jan Kara.
Link: https://lore.kernel.org/20260625153853.913949-1-pfalcato@suse.de
Fixes:
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SeongJae Park
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35d4a3cf70 |
mm/damon/ops-common: handle extreme intervals in damon_hot_score()
Fix three issues in damon_hot_score() that comes from wrong handling of
extreme (zero or too high) monitoring intervals user setup.
When the user sets sampling interval zero, damon_max_nr_accesses(), which
is called from damon_hot_score(), causes a divide-by-zero. Needless to
say, it is a problem.
When the user sets the aggregation interval zero, the function returns
zero. It is wrong, since the real maximum nr_acceses in the setup should
be one. Worse yet, it can cause another divide-by-zero from its caller,
damon_hot_score(), since it uses damon_max_nr_accesses() return value as a
denominator.
When the user sets the aggregation interval very high, damon_hot_score()
could return a value out of [0, DAMOS_MAX_SCORE] range. Since the return
value is used as an index to the regions_score_histogram array, which is
DAMOS_MAX_SCORE+1 size, it causes out of bounds array access.
The issues can be relatively easily reproduced like below. The sysfs
write permission is required, though.
# ./damo start --damos_action lru_prio --damos_quota_space 100M \
--damos_quota_interval 1s
# cd /sys/kernel/mm/damon/admin/kdamonds/0
# echo 0 > contexts/0/monitoring_attrs/intervals/sample_us
# echo 0 > contexts/0/monitoring_attrs/intervals/aggr_us
# echo commit > state
# dmesg
[...]
[ 131.329762] Oops: divide error: 0000 [#1] SMP NOPTI
[...]
[ 131.336089] RIP: 0010:damon_hot_score+0x27/0xd0
[...]
Fix the divide-by-zero intervals problems by explicitly handling the zero
intervals in damon_max_nr_accesses(). Fix the out-of-bound array access
by applying [0, DAMOS_MAX_SCORE] bounds before returning from
damon_hot_score().
The issue was discovered [1] by Sashiko.
Link: https://lore.kernel.org/20260623135834.67189-1-sj@kernel.org
Link: https://lore.kernel.org/20260619202459.145010-1-sj@kernel.org [1]
Fixes:
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Zi Yan
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7da7d599b8 |
mm/compaction: handle free_pages_prepare() properly in compaction_free()
free_pages_prepare() can fail but compaction_free() does not handle the
failure case. Failed pages should not be added back to cc->freepages for
future use, since they can be either PageHWPoison or free_page_is_bad()
and might cause data corruption.
Link: https://lore.kernel.org/20260622-handle_free_pages_prepare_in_compaction_free-v1-1-fcf3b14abcf7@nvidia.com
Fixes:
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