Pull MM updates from Andrew Morton:
- "mm, swap: improve cluster scan strategy" from Kairui Song improves
performance and reduces the failure rate of swap cluster allocation
- "support large align and nid in Rust allocators" from Vitaly Wool
permits Rust allocators to set NUMA node and large alignment when
perforning slub and vmalloc reallocs
- "mm/damon/vaddr: support stat-purpose DAMOS" from Yueyang Pan extend
DAMOS_STAT's handling of the DAMON operations sets for virtual
address spaces for ops-level DAMOS filters
- "execute PROCMAP_QUERY ioctl under per-vma lock" from Suren
Baghdasaryan reduces mmap_lock contention during reads of
/proc/pid/maps
- "mm/mincore: minor clean up for swap cache checking" from Kairui Song
performs some cleanup in the swap code
- "mm: vm_normal_page*() improvements" from David Hildenbrand provides
code cleanup in the pagemap code
- "add persistent huge zero folio support" from Pankaj Raghav provides
a block layer speedup by optionalls making the
huge_zero_pagepersistent, instead of releasing it when its refcount
falls to zero
- "kho: fixes and cleanups" from Mike Rapoport adds a few touchups to
the recently added Kexec Handover feature
- "mm: make mm->flags a bitmap and 64-bit on all arches" from Lorenzo
Stoakes turns mm_struct.flags into a bitmap. To end the constant
struggle with space shortage on 32-bit conflicting with 64-bit's
needs
- "mm/swapfile.c and swap.h cleanup" from Chris Li cleans up some swap
code
- "selftests/mm: Fix false positives and skip unsupported tests" from
Donet Tom fixes a few things in our selftests code
- "prctl: extend PR_SET_THP_DISABLE to only provide THPs when advised"
from David Hildenbrand "allows individual processes to opt-out of
THP=always into THP=madvise, without affecting other workloads on the
system".
It's a long story - the [1/N] changelog spells out the considerations
- "Add and use memdesc_flags_t" from Matthew Wilcox gets us started on
the memdesc project. Please see
https://kernelnewbies.org/MatthewWilcox/Memdescs and
https://blogs.oracle.com/linux/post/introducing-memdesc
- "Tiny optimization for large read operations" from Chi Zhiling
improves the efficiency of the pagecache read path
- "Better split_huge_page_test result check" from Zi Yan improves our
folio splitting selftest code
- "test that rmap behaves as expected" from Wei Yang adds some rmap
selftests
- "remove write_cache_pages()" from Christoph Hellwig removes that
function and converts its two remaining callers
- "selftests/mm: uffd-stress fixes" from Dev Jain fixes some UFFD
selftests issues
- "introduce kernel file mapped folios" from Boris Burkov introduces
the concept of "kernel file pages". Using these permits btrfs to
account its metadata pages to the root cgroup, rather than to the
cgroups of random inappropriate tasks
- "mm/pageblock: improve readability of some pageblock handling" from
Wei Yang provides some readability improvements to the page allocator
code
- "mm/damon: support ARM32 with LPAE" from SeongJae Park teaches DAMON
to understand arm32 highmem
- "tools: testing: Use existing atomic.h for vma/maple tests" from
Brendan Jackman performs some code cleanups and deduplication under
tools/testing/
- "maple_tree: Fix testing for 32bit compiles" from Liam Howlett fixes
a couple of 32-bit issues in tools/testing/radix-tree.c
- "kasan: unify kasan_enabled() and remove arch-specific
implementations" from Sabyrzhan Tasbolatov moves KASAN arch-specific
initialization code into a common arch-neutral implementation
- "mm: remove zpool" from Johannes Weiner removes zspool - an
indirection layer which now only redirects to a single thing
(zsmalloc)
- "mm: task_stack: Stack handling cleanups" from Pasha Tatashin makes a
couple of cleanups in the fork code
- "mm: remove nth_page()" from David Hildenbrand makes rather a lot of
adjustments at various nth_page() callsites, eventually permitting
the removal of that undesirable helper function
- "introduce kasan.write_only option in hw-tags" from Yeoreum Yun
creates a KASAN read-only mode for ARM, using that architecture's
memory tagging feature. It is felt that a read-only mode KASAN is
suitable for use in production systems rather than debug-only
- "mm: hugetlb: cleanup hugetlb folio allocation" from Kefeng Wang does
some tidying in the hugetlb folio allocation code
- "mm: establish const-correctness for pointer parameters" from Max
Kellermann makes quite a number of the MM API functions more accurate
about the constness of their arguments. This was getting in the way
of subsystems (in this case CEPH) when they attempt to improving
their own const/non-const accuracy
- "Cleanup free_pages() misuse" from Vishal Moola fixes a number of
code sites which were confused over when to use free_pages() vs
__free_pages()
- "Add Rust abstraction for Maple Trees" from Alice Ryhl makes the
mapletree code accessible to Rust. Required by nouveau and by its
forthcoming successor: the new Rust Nova driver
- "selftests/mm: split_huge_page_test: split_pte_mapped_thp
improvements" from David Hildenbrand adds a fix and some cleanups to
the thp selftesting code
- "mm, swap: introduce swap table as swap cache (phase I)" from Chris
Li and Kairui Song is the first step along the path to implementing
"swap tables" - a new approach to swap allocation and state tracking
which is expected to yield speed and space improvements. This
patchset itself yields a 5-20% performance benefit in some situations
- "Some ptdesc cleanups" from Matthew Wilcox utilizes the new memdesc
layer to clean up the ptdesc code a little
- "Fix va_high_addr_switch.sh test failure" from Chunyu Hu fixes some
issues in our 5-level pagetable selftesting code
- "Minor fixes for memory allocation profiling" from Suren Baghdasaryan
addresses a couple of minor issues in relatively new memory
allocation profiling feature
- "Small cleanups" from Matthew Wilcox has a few cleanups in
preparation for more memdesc work
- "mm/damon: add addr_unit for DAMON_LRU_SORT and DAMON_RECLAIM" from
Quanmin Yan makes some changes to DAMON in furtherance of supporting
arm highmem
- "selftests/mm: Add -Wunreachable-code and fix warnings" from Muhammad
Anjum adds that compiler check to selftests code and fixes the
fallout, by removing dead code
- "Improvements to Victim Process Thawing and OOM Reaper Traversal
Order" from zhongjinji makes a number of improvements in the OOM
killer: mainly thawing a more appropriate group of victim threads so
they can release resources
- "mm/damon: misc fixups and improvements for 6.18" from SeongJae Park
is a bunch of small and unrelated fixups for DAMON
- "mm/damon: define and use DAMON initialization check function" from
SeongJae Park implement reliability and maintainability improvements
to a recently-added bug fix
- "mm/damon/stat: expose auto-tuned intervals and non-idle ages" from
SeongJae Park provides additional transparency to userspace clients
of the DAMON_STAT information
- "Expand scope of khugepaged anonymous collapse" from Dev Jain removes
some constraints on khubepaged's collapsing of anon VMAs. It also
increases the success rate of MADV_COLLAPSE against an anon vma
- "mm: do not assume file == vma->vm_file in compat_vma_mmap_prepare()"
from Lorenzo Stoakes moves us further towards removal of
file_operations.mmap(). This patchset concentrates upon clearing up
the treatment of stacked filesystems
- "mm: Improve mlock tracking for large folios" from Kiryl Shutsemau
provides some fixes and improvements to mlock's tracking of large
folios. /proc/meminfo's "Mlocked" field became more accurate
- "mm/ksm: Fix incorrect accounting of KSM counters during fork" from
Donet Tom fixes several user-visible KSM stats inaccuracies across
forks and adds selftest code to verify these counters
- "mm_slot: fix the usage of mm_slot_entry" from Wei Yang addresses
some potential but presently benign issues in KSM's mm_slot handling
* tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (372 commits)
mm: swap: check for stable address space before operating on the VMA
mm: convert folio_page() back to a macro
mm/khugepaged: use start_addr/addr for improved readability
hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list
alloc_tag: fix boot failure due to NULL pointer dereference
mm: silence data-race in update_hiwater_rss
mm/memory-failure: don't select MEMORY_ISOLATION
mm/khugepaged: remove definition of struct khugepaged_mm_slot
mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL
hugetlb: increase number of reserving hugepages via cmdline
selftests/mm: add fork inheritance test for ksm_merging_pages counter
mm/ksm: fix incorrect KSM counter handling in mm_struct during fork
drivers/base/node: fix double free in register_one_node()
mm: remove PMD alignment constraint in execmem_vmalloc()
mm/memory_hotplug: fix typo 'esecially' -> 'especially'
mm/rmap: improve mlock tracking for large folios
mm/filemap: map entire large folio faultaround
mm/fault: try to map the entire file folio in finish_fault()
mm/rmap: mlock large folios in try_to_unmap_one()
mm/rmap: fix a mlock race condition in folio_referenced_one()
...
kmalloc_nolock() relies on ability of local_trylock_t to detect
the situation when per-cpu kmem_cache is locked.
In !PREEMPT_RT local_(try)lock_irqsave(&s->cpu_slab->lock, flags)
disables IRQs and marks s->cpu_slab->lock as acquired.
local_lock_is_locked(&s->cpu_slab->lock) returns true when
slab is in the middle of manipulating per-cpu cache
of that specific kmem_cache.
kmalloc_nolock() can be called from any context and can re-enter
into ___slab_alloc():
kmalloc() -> ___slab_alloc(cache_A) -> irqsave -> NMI -> bpf ->
kmalloc_nolock() -> ___slab_alloc(cache_B)
or
kmalloc() -> ___slab_alloc(cache_A) -> irqsave -> tracepoint/kprobe -> bpf ->
kmalloc_nolock() -> ___slab_alloc(cache_B)
Hence the caller of ___slab_alloc() checks if &s->cpu_slab->lock
can be acquired without a deadlock before invoking the function.
If that specific per-cpu kmem_cache is busy the kmalloc_nolock()
retries in a different kmalloc bucket. The second attempt will
likely succeed, since this cpu locked different kmem_cache.
Similarly, in PREEMPT_RT local_lock_is_locked() returns true when
per-cpu rt_spin_lock is locked by current _task_. In this case
re-entrance into the same kmalloc bucket is unsafe, and
kmalloc_nolock() tries a different bucket that is most likely is
not locked by the current task. Though it may be locked by a
different task it's safe to rt_spin_lock() and sleep on it.
Similar to alloc_pages_nolock() the kmalloc_nolock() returns NULL
immediately if called from hard irq or NMI in PREEMPT_RT.
kfree_nolock() defers freeing to irq_work when local_lock_is_locked()
and (in_nmi() or in PREEMPT_RT).
SLUB_TINY config doesn't use local_lock_is_locked() and relies on
spin_trylock_irqsave(&n->list_lock) to allocate,
while kfree_nolock() always defers to irq_work.
Note, kfree_nolock() must be called _only_ for objects allocated
with kmalloc_nolock(). Debug checks (like kmemleak and kfence)
were skipped on allocation, hence obj = kmalloc(); kfree_nolock(obj);
will miss kmemleak/kfence book keeping and will cause false positives.
large_kmalloc is not supported by either kmalloc_nolock()
or kfree_nolock().
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Patch series "kasan: unify kasan_enabled() and remove arch-specific
implementations", v6.
This patch series addresses the fragmentation in KASAN initialization
across architectures by introducing a unified approach that eliminates
duplicate static keys and arch-specific kasan_arch_is_ready()
implementations.
The core issue is that different architectures have inconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions
or always-on behavior
This patch (of 2):
Introduce CONFIG_ARCH_DEFER_KASAN to identify architectures [1] that need
to defer KASAN initialization until shadow memory is properly set up, and
unify the static key infrastructure across all KASAN modes.
[1] PowerPC, UML, LoongArch selects ARCH_DEFER_KASAN.
The core issue is that different architectures haveinconsistent approaches
to KASAN readiness tracking:
- PowerPC, LoongArch, and UML arch, each implement own
kasan_arch_is_ready()
- Only HW_TAGS mode had a unified static key (kasan_flag_enabled)
- Generic and SW_TAGS modes relied on arch-specific solutions or always-on
behavior
This patch addresses the fragmentation in KASAN initialization across
architectures by introducing a unified approach that eliminates duplicate
static keys and arch-specific kasan_arch_is_ready() implementations.
Let's replace kasan_arch_is_ready() with existing kasan_enabled() check,
which examines the static key being enabled if arch selects
ARCH_DEFER_KASAN or has HW_TAGS mode support. For other arch,
kasan_enabled() checks the enablement during compile time.
Now KASAN users can use a single kasan_enabled() check everywhere.
Link: https://lkml.kernel.org/r/20250810125746.1105476-1-snovitoll@gmail.com
Link: https://lkml.kernel.org/r/20250810125746.1105476-2-snovitoll@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217049
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> #powerpc
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Gow <davidgow@google.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: Marco Elver <elver@google.com>
Cc: Qing Zhang <zhangqing@loongson.cn>
Cc: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, enabling KASAN masks bugs where a lockless lookup path gets a
pointer to a SLAB_TYPESAFE_BY_RCU object that might concurrently be
recycled and is insufficiently careful about handling recycled objects:
KASAN puts freed objects in SLAB_TYPESAFE_BY_RCU slabs onto its quarantine
queues, even when it can't actually detect UAF in these objects, and the
quarantine prevents fast recycling.
When I introduced CONFIG_SLUB_RCU_DEBUG, my intention was that enabling
CONFIG_SLUB_RCU_DEBUG should cause KASAN to mark such objects as freed
after an RCU grace period and put them on the quarantine, while disabling
CONFIG_SLUB_RCU_DEBUG should allow such objects to be reused immediately;
but that hasn't actually been working.
I discovered such a UAF bug involving SLAB_TYPESAFE_BY_RCU yesterday; I
could only trigger this bug in a KASAN build by disabling
CONFIG_SLUB_RCU_DEBUG and applying this patch.
Link: https://lkml.kernel.org/r/20250723-kasan-tsbrcu-noquarantine-v1-1-846c8645976c@google.com
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Alexander Potapenko <glider@google.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, KASAN is unable to catch use-after-free in SLAB_TYPESAFE_BY_RCU
slabs because use-after-free is allowed within the RCU grace period by
design.
Add a SLUB debugging feature which RCU-delays every individual
kmem_cache_free() before either actually freeing the object or handing it
off to KASAN, and change KASAN to poison freed objects as normal when this
option is enabled.
For now I've configured Kconfig.debug to default-enable this feature in the
KASAN GENERIC and SW_TAGS modes; I'm not enabling it by default in HW_TAGS
mode because I'm not sure if it might have unwanted performance degradation
effects there.
Note that this is mostly useful with KASAN in the quarantine-based GENERIC
mode; SLAB_TYPESAFE_BY_RCU slabs are basically always also slabs with a
->ctor, and KASAN's assign_tag() currently has to assign fixed tags for
those, reducing the effectiveness of SW_TAGS/HW_TAGS mode.
(A possible future extension of this work would be to also let SLUB call
the ->ctor() on every allocation instead of only when the slab page is
allocated; then tag-based modes would be able to assign new tags on every
reallocation.)
Tested-by: syzbot+263726e59eab6b442723@syzkaller.appspotmail.com
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Acked-by: Marco Elver <elver@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz> #slab
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Currently, when KASAN is combined with init-on-free behavior, the
initialization happens before KASAN's "invalid free" checks.
More importantly, a subsequent commit will want to RCU-delay the actual
SLUB freeing of an object, and we'd like KASAN to still validate
synchronously that freeing the object is permitted. (Otherwise this
change will make the existing testcase kmem_cache_invalid_free fail.)
So add a new KASAN hook that allows KASAN to pre-validate a
kmem_cache_free() operation before SLUB actually starts modifying the
object or its metadata.
Inside KASAN, this:
- moves checks from poison_slab_object() into check_slab_allocation()
- moves kasan_arch_is_ready() up into callers of poison_slab_object()
- removes "ip" argument of poison_slab_object() and __kasan_slab_free()
(since those functions no longer do any reporting)
Acked-by: Vlastimil Babka <vbabka@suse.cz> #slub
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This partially reverts commits cc478e0b6b, 63b85ac56a, 08d7c94d96,
a414d4286f, and 773688a6cb to make use of variable-sized stack depot
records, since eviction of stack entries from stack depot forces fixed-
sized stack records. Care was taken to retain the code cleanups by the
above commits.
Eviction was added to generic KASAN as a response to alleviating the
additional memory usage from fixed-sized stack records, but this still
uses more memory than previously.
With the re-introduction of variable-sized records for stack depot, we can
just switch back to non-evictable stack records again, and return back to
the previous performance and memory usage baseline.
Before (observed after a KASAN kernel boot):
pools: 597
refcounted_allocations: 17547
refcounted_frees: 6477
refcounted_in_use: 11070
freelist_size: 3497
persistent_count: 12163
persistent_bytes: 1717008
After:
pools: 319
refcounted_allocations: 0
refcounted_frees: 0
refcounted_in_use: 0
freelist_size: 0
persistent_count: 29397
persistent_bytes: 5183536
As can be seen from the counters, with a generic KASAN config, refcounted
allocations and evictions are no longer used. Due to using variable-sized
records, I observe a reduction of 278 stack depot pools (saving 4448 KiB)
with my test setup.
Link: https://lkml.kernel.org/r/20240129100708.39460-2-elver@google.com
Fixes: cc478e0b6b ("kasan: avoid resetting aux_lock")
Fixes: 63b85ac56a ("kasan: stop leaking stack trace handles")
Fixes: 08d7c94d96 ("kasan: memset free track in qlink_free")
Fixes: a414d4286f ("kasan: handle concurrent kasan_record_aux_stack calls")
Fixes: 773688a6cb ("kasan: use stack_depot_put for Generic mode")
Signed-off-by: Marco Elver <elver@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In 5d4c6ac946 ("kasan: record and report more information") I thought
that printk only displays a maximum of 99999 seconds, but actually printk
can display a larger number of seconds.
So increase the number of bits to shift when recording the extra timestamp
(44 bits), without affecting the precision, shift it right by 9 bits,
discarding all bits that do not affect the microsecond part (nanoseconds
will not be shown).
Currently the maximum time that can be displayed is 9007199.254740s,
because
11111111111111111111111111111111111111111111 (44 bits) << 9
= 11111111111111111111111111111111111111111111000000000
= 9007199.254740
Link: https://lkml.kernel.org/r/AM6PR03MB58481629F2F28CE007412139994D2@AM6PR03MB5848.eurprd03.prod.outlook.com
Fixes: 5d4c6ac946 ("kasan: record and report more information")
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Pull MM updates from Andrew Morton:
"Many singleton patches against the MM code. The patch series which are
included in this merge do the following:
- Peng Zhang has done some mapletree maintainance work in the series
'maple_tree: add mt_free_one() and mt_attr() helpers'
'Some cleanups of maple tree'
- In the series 'mm: use memmap_on_memory semantics for dax/kmem'
Vishal Verma has altered the interworking between memory-hotplug
and dax/kmem so that newly added 'device memory' can more easily
have its memmap placed within that newly added memory.
- Matthew Wilcox continues folio-related work (including a few fixes)
in the patch series
'Add folio_zero_tail() and folio_fill_tail()'
'Make folio_start_writeback return void'
'Fix fault handler's handling of poisoned tail pages'
'Convert aops->error_remove_page to ->error_remove_folio'
'Finish two folio conversions'
'More swap folio conversions'
- Kefeng Wang has also contributed folio-related work in the series
'mm: cleanup and use more folio in page fault'
- Jim Cromie has improved the kmemleak reporting output in the series
'tweak kmemleak report format'.
- In the series 'stackdepot: allow evicting stack traces' Andrey
Konovalov to permits clients (in this case KASAN) to cause eviction
of no longer needed stack traces.
- Charan Teja Kalla has fixed some accounting issues in the page
allocator's atomic reserve calculations in the series 'mm:
page_alloc: fixes for high atomic reserve caluculations'.
- Dmitry Rokosov has added to the samples/ dorectory some sample code
for a userspace memcg event listener application. See the series
'samples: introduce cgroup events listeners'.
- Some mapletree maintanance work from Liam Howlett in the series
'maple_tree: iterator state changes'.
- Nhat Pham has improved zswap's approach to writeback in the series
'workload-specific and memory pressure-driven zswap writeback'.
- DAMON/DAMOS feature and maintenance work from SeongJae Park in the
series
'mm/damon: let users feed and tame/auto-tune DAMOS'
'selftests/damon: add Python-written DAMON functionality tests'
'mm/damon: misc updates for 6.8'
- Yosry Ahmed has improved memcg's stats flushing in the series 'mm:
memcg: subtree stats flushing and thresholds'.
- In the series 'Multi-size THP for anonymous memory' Ryan Roberts
has added a runtime opt-in feature to transparent hugepages which
improves performance by allocating larger chunks of memory during
anonymous page faults.
- Matthew Wilcox has also contributed some cleanup and maintenance
work against eh buffer_head code int he series 'More buffer_head
cleanups'.
- Suren Baghdasaryan has done work on Andrea Arcangeli's series
'userfaultfd move option'. UFFDIO_MOVE permits userspace heap
compaction algorithms to move userspace's pages around rather than
UFFDIO_COPY'a alloc/copy/free.
- Stefan Roesch has developed a 'KSM Advisor', in the series 'mm/ksm:
Add ksm advisor'. This is a governor which tunes KSM's scanning
aggressiveness in response to userspace's current needs.
- Chengming Zhou has optimized zswap's temporary working memory use
in the series 'mm/zswap: dstmem reuse optimizations and cleanups'.
- Matthew Wilcox has performed some maintenance work on the writeback
code, both code and within filesystems. The series is 'Clean up the
writeback paths'.
- Andrey Konovalov has optimized KASAN's handling of alloc and free
stack traces for secondary-level allocators, in the series 'kasan:
save mempool stack traces'.
- Andrey also performed some KASAN maintenance work in the series
'kasan: assorted clean-ups'.
- David Hildenbrand has gone to town on the rmap code. Cleanups, more
pte batching, folio conversions and more. See the series 'mm/rmap:
interface overhaul'.
- Kinsey Ho has contributed some maintenance work on the MGLRU code
in the series 'mm/mglru: Kconfig cleanup'.
- Matthew Wilcox has contributed lruvec page accounting code cleanups
in the series 'Remove some lruvec page accounting functions'"
* tag 'mm-stable-2024-01-08-15-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (361 commits)
mm, treewide: rename MAX_ORDER to MAX_PAGE_ORDER
mm, treewide: introduce NR_PAGE_ORDERS
selftests/mm: add separate UFFDIO_MOVE test for PMD splitting
selftests/mm: skip test if application doesn't has root privileges
selftests/mm: conform test to TAP format output
selftests: mm: hugepage-mmap: conform to TAP format output
selftests/mm: gup_test: conform test to TAP format output
mm/selftests: hugepage-mremap: conform test to TAP format output
mm/vmstat: move pgdemote_* out of CONFIG_NUMA_BALANCING
mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large
mm/memcontrol: remove __mod_lruvec_page_state()
mm/khugepaged: use a folio more in collapse_file()
slub: use a folio in __kmalloc_large_node
slub: use folio APIs in free_large_kmalloc()
slub: use alloc_pages_node() in alloc_slab_page()
mm: remove inc/dec lruvec page state functions
mm: ratelimit stat flush from workingset shrinker
kasan: stop leaking stack trace handles
mm/mglru: remove CONFIG_TRANSPARENT_HUGEPAGE
mm/mglru: add dummy pmd_dirty()
...
Commit 773688a6cb ("kasan: use stack_depot_put for Generic mode") added
support for stack trace eviction for Generic KASAN.
However, that commit didn't evict stack traces when the object is not put
into quarantine. As a result, some stack traces are never evicted from
the stack depot.
In addition, with the "kasan: save mempool stack traces" series, the free
stack traces for mempool objects are also not properly evicted from the
stack depot.
Fix both issues by:
1. Evicting all stack traces when an object if freed if it was not put
into quarantine;
2. Always evicting an existing free stack trace when a new one is saved.
Also do a few related clean-ups:
- Do not zero out free track when initializing/invalidating free meta:
set a value in shadow memory instead;
- Rename KASAN_SLAB_FREETRACK to KASAN_SLAB_FREE_META;
- Drop the kasan_init_cache_meta function as it's not used by KASAN;
- Add comments for the kasan_alloc_meta and kasan_free_meta structs.
[akpm@linux-foundation.org: make release_free_meta() and release_alloc_meta() static]
Link: https://lkml.kernel.org/r/20231226225121.235865-1-andrey.konovalov@linux.dev
Fixes: 773688a6cb ("kasan: use stack_depot_put for Generic mode")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "kasan: save mempool stack traces".
This series updates KASAN to save alloc and free stack traces for
secondary-level allocators that cache and reuse allocations internally
instead of giving them back to the underlying allocator (e.g. mempool).
As a part of this change, introduce and document a set of KASAN hooks:
bool kasan_mempool_poison_pages(struct page *page, unsigned int order);
void kasan_mempool_unpoison_pages(struct page *page, unsigned int order);
bool kasan_mempool_poison_object(void *ptr);
void kasan_mempool_unpoison_object(void *ptr, size_t size);
and use them in the mempool code.
Besides mempool, skbuff and io_uring also cache allocations and already
use KASAN hooks to poison those. Their code is updated to use the new
mempool hooks.
The new hooks save alloc and free stack traces (for normal kmalloc and
slab objects; stack traces for large kmalloc objects and page_alloc are
not supported by KASAN yet), improve the readability of the users' code,
and also allow the users to prevent double-free and invalid-free bugs; see
the patches for the details.
This patch (of 21):
Rename kasan_slab_free_mempool to kasan_mempool_poison_object.
kasan_slab_free_mempool is a slightly confusing name: it is unclear
whether this function poisons the object when it is freed into mempool or
does something when the object is freed from mempool to the underlying
allocator.
The new name also aligns with other mempool-related KASAN hooks added in
the following patches in this series.
Link: https://lkml.kernel.org/r/cover.1703024586.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/c5618685abb7cdbf9fb4897f565e7759f601da84.1703024586.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Lobakin <alobakin@pm.me>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Record and report more information to help us find the cause of the bug
and to help us correlate the error with other system events.
This patch adds recording and showing CPU number and timestamp at
allocation and free (controlled by CONFIG_KASAN_EXTRA_INFO). The
timestamps in the report use the same format and source as printk.
Error occurrence timestamp is already implicit in the printk log, and CPU
number is already shown by dump_stack_lvl, so there is no need to add it.
In order to record CPU number and timestamp at allocation and free,
corresponding members need to be added to the relevant data structures,
which will lead to increased memory consumption.
In Generic KASAN, members are added to struct kasan_track. Since in most
cases, alloc meta is stored in the redzone and free meta is stored in the
object or the redzone, memory consumption will not increase much.
In SW_TAGS KASAN and HW_TAGS KASAN, members are added to struct
kasan_stack_ring_entry. Memory consumption increases as the size of
struct kasan_stack_ring_entry increases (this part of the memory is
allocated by memblock), but since this is configurable, it is up to the
user to choose.
Link: https://lkml.kernel.org/r/VI1P193MB0752BD991325D10E4AB1913599BDA@VI1P193MB0752.EURP193.PROD.OUTLOOK.COM
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Evict alloc/free stack traces from the stack depot for Generic KASAN once
they are evicted from the quaratine.
For auxiliary stack traces, evict the oldest stack trace once a new one is
saved (KASAN only keeps references to the last two).
Also evict all saved stack traces on krealloc.
To avoid double-evicting and mis-evicting stack traces (in case KASAN's
metadata was corrupted), reset KASAN's per-object metadata that stores
stack depot handles when the object is initialized and when it's evicted
from the quarantine.
Note that stack_depot_put is no-op if the handle is 0.
Link: https://lkml.kernel.org/r/5cef104d9b842899489b4054fe8d1339a71acee0.1700502145.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
gcc-13 warns about function definitions for builtin interfaces that have a
different prototype, e.g.:
In file included from kasan_test.c:31:
kasan.h:574:6: error: conflicting types for built-in function '__asan_register_globals'; expected 'void(void *, long int)' [-Werror=builtin-declaration-mismatch]
574 | void __asan_register_globals(struct kasan_global *globals, size_t size);
kasan.h:577:6: error: conflicting types for built-in function '__asan_alloca_poison'; expected 'void(void *, long int)' [-Werror=builtin-declaration-mismatch]
577 | void __asan_alloca_poison(unsigned long addr, size_t size);
kasan.h:580:6: error: conflicting types for built-in function '__asan_load1'; expected 'void(void *)' [-Werror=builtin-declaration-mismatch]
580 | void __asan_load1(unsigned long addr);
kasan.h:581:6: error: conflicting types for built-in function '__asan_store1'; expected 'void(void *)' [-Werror=builtin-declaration-mismatch]
581 | void __asan_store1(unsigned long addr);
kasan.h:643:6: error: conflicting types for built-in function '__hwasan_tag_memory'; expected 'void(void *, unsigned char, long int)' [-Werror=builtin-declaration-mismatch]
643 | void __hwasan_tag_memory(unsigned long addr, u8 tag, unsigned long size);
The two problems are:
- Addresses are passes as 'unsigned long' in the kernel, but gcc-13
expects a 'void *'.
- sizes meant to use a signed ssize_t rather than size_t.
Change all the prototypes to match these. Using 'void *' consistently for
addresses gets rid of a couple of type casts, so push that down to the
leaf functions where possible.
This now passes all randconfig builds on arm, arm64 and x86, but I have
not tested it on the other architectures that support kasan, since they
tend to fail randconfig builds in other ways. This might fail if any of
the 32-bit architectures expect a 'long' instead of 'int' for the size
argument.
The __asan_allocas_unpoison() function prototype is somewhat weird, since
it uses a pointer for 'stack_top' and an size_t for 'stack_bottom'. This
looks like it is meant to be 'addr' and 'size' like the others, but the
implementation clearly treats them as 'top' and 'bottom'.
Link: https://lkml.kernel.org/r/20230509145735.9263-2-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The current implementation of the extra_bits interface is confusing:
passing extra_bits to __stack_depot_save makes it seem that the extra
bits are somehow stored in stack depot. In reality, they are only
embedded into a stack depot handle and are not used within stack depot.
Drop the extra_bits argument from __stack_depot_save and instead provide
a new stack_depot_set_extra_bits function (similar to the exsiting
stack_depot_get_extra_bits) that saves extra bits into a stack depot
handle.
Update the callers of __stack_depot_save to use the new interace.
This change also fixes a minor issue in the old code: __stack_depot_save
does not return NULL if saving stack trace fails and extra_bits is used.
Link: https://lkml.kernel.org/r/317123b5c05e2f82854fc55d8b285e0869d3cb77.1676063693.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
As Hardware Tag-Based KASAN is intended to be used in production, its
performance impact is crucial. As page_alloc allocations tend to be big,
tagging and checking all such allocations can introduce a significant
slowdown.
Add two new boot parameters that allow to alleviate that slowdown:
- kasan.page_alloc.sample, which makes Hardware Tag-Based KASAN tag only
every Nth page_alloc allocation with the order configured by the second
added parameter (default: tag every such allocation).
- kasan.page_alloc.sample.order, which makes sampling enabled by the first
parameter only affect page_alloc allocations with the order equal or
greater than the specified value (default: 3, see below).
The exact performance improvement caused by using the new parameters
depends on their values and the applied workload.
The chosen default value for kasan.page_alloc.sample.order is 3, which
matches both PAGE_ALLOC_COSTLY_ORDER and SKB_FRAG_PAGE_ORDER. This is
done for two reasons:
1. PAGE_ALLOC_COSTLY_ORDER is "the order at which allocations are deemed
costly to service", which corresponds to the idea that only large and
thus costly allocations are supposed to sampled.
2. One of the workloads targeted by this patch is a benchmark that sends
a large amount of data over a local loopback connection. Most multi-page
data allocations in the networking subsystem have the order of
SKB_FRAG_PAGE_ORDER (or PAGE_ALLOC_COSTLY_ORDER).
When running a local loopback test on a testing MTE-enabled device in sync
mode, enabling Hardware Tag-Based KASAN introduces a ~50% slowdown.
Applying this patch and setting kasan.page_alloc.sampling to a value
higher than 1 allows to lower the slowdown. The performance improvement
saturates around the sampling interval value of 10 with the default
sampling page order of 3. This lowers the slowdown to ~20%. The slowdown
in real scenarios involving the network will likely be better.
Enabling page_alloc sampling has a downside: KASAN misses bad accesses to
a page_alloc allocation that has not been tagged. This lowers the value
of KASAN as a security mitigation.
However, based on measuring the number of page_alloc allocations of
different orders during boot in a test build, sampling with the default
kasan.page_alloc.sample.order value affects only ~7% of allocations. The
rest ~93% of allocations are still checked deterministically.
Link: https://lkml.kernel.org/r/129da0614123bb85ed4dd61ae30842b2dd7c903f.1671471846.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mark Brand <markbrand@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Right now, kasan_cache_create() assigns SLAB_KASAN for all KASAN modes and
then sets up metadata-related cache parameters for the Generic mode.
SLAB_KASAN is used in two places:
1. In slab_ksize() to account for per-object metadata when
calculating the size of the accessible memory within the object.
2. In slab_common.c via kasan_never_merge() to prevent merging of
caches with per-object metadata.
Both cases are only relevant when per-object metadata is present, which is
only the case with the Generic mode.
Thus, assign SLAB_KASAN and define kasan_cache_create() only for the
Generic mode.
Also update the SLAB_KASAN-related comment.
Link: https://lkml.kernel.org/r/61faa2aa1906e2d02c97d00ddf99ce8911dda095.1662411799.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "kasan: switch tag-based modes to stack ring from per-object
metadata", v3.
This series makes the tag-based KASAN modes use a ring buffer for storing
stack depot handles for alloc/free stack traces for slab objects instead
of per-object metadata. This ring buffer is referred to as the stack
ring.
On each alloc/free of a slab object, the tagged address of the object and
the current stack trace are recorded in the stack ring.
On each bug report, if the accessed address belongs to a slab object, the
stack ring is scanned for matching entries. The newest entries are used
to print the alloc/free stack traces in the report: one entry for alloc
and one for free.
The advantages of this approach over storing stack trace handles in
per-object metadata with the tag-based KASAN modes:
- Allows to find relevant stack traces for use-after-free bugs without
using quarantine for freed memory. (Currently, if the object was
reallocated multiple times, the report contains the latest alloc/free
stack traces, not necessarily the ones relevant to the buggy allocation.)
- Allows to better identify and mark use-after-free bugs, effectively
making the CONFIG_KASAN_TAGS_IDENTIFY functionality always-on.
- Has fixed memory overhead.
The disadvantage:
- If the affected object was allocated/freed long before the bug happened
and the stack trace events were purged from the stack ring, the report
will have no stack traces.
Discussion
==========
The proposed implementation of the stack ring uses a single ring buffer
for the whole kernel. This might lead to contention due to atomic
accesses to the ring buffer index on multicore systems.
At this point, it is unknown whether the performance impact from this
contention would be significant compared to the slowdown introduced by
collecting stack traces due to the planned changes to the latter part, see
the section below.
For now, the proposed implementation is deemed to be good enough, but this
might need to be revisited once the stack collection becomes faster.
A considered alternative is to keep a separate ring buffer for each CPU
and then iterate over all of them when printing a bug report. This
approach requires somehow figuring out which of the stack rings has the
freshest stack traces for an object if multiple stack rings have them.
Further plans
=============
This series is a part of an effort to make KASAN stack trace collection
suitable for production. This requires stack trace collection to be fast
and memory-bounded.
The planned steps are:
1. Speed up stack trace collection (potentially, by using SCS;
patches on-hold until steps #2 and #3 are completed).
2. Keep stack trace handles in the stack ring (this series).
3. Add a memory-bounded mode to stack depot or provide an alternative
memory-bounded stack storage.
4. Potentially, implement stack trace collection sampling to minimize
the performance impact.
This patch (of 34):
__kasan_metadata_size() calculates the size of the redzone for objects in
a slab cache.
When accounting for presence of kasan_free_meta in the redzone, this
function only compares free_meta_offset with 0. But free_meta_offset
could also be equal to KASAN_NO_FREE_META, which indicates that
kasan_free_meta is not present at all.
Add a comparison with KASAN_NO_FREE_META into __kasan_metadata_size().
Link: https://lkml.kernel.org/r/cover.1662411799.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/c7b316d30d90e5947eb8280f4dc78856a49298cf.1662411799.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
