Pull sysctl table constification from Joel Granados:
"All ctl_table declared outside of functions and that remain unmodified
after initialization are const qualified.
This prevents unintended modifications to proc_handler function
pointers by placing them in the .rodata section.
This is a continuation of the tree-wide effort started a few releases
ago with the constification of the ctl_table struct arguments in the
sysctl API done in 78eb4ea25c ("sysctl: treewide: constify the
ctl_table argument of proc_handlers")"
* tag 'constfy-sysctl-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/sysctl/sysctl:
treewide: const qualify ctl_tables where applicable
Pull driver core and debugfs updates from Greg KH:
"Here is the big set of driver core and debugfs updates for 6.14-rc1.
Included in here is a bunch of driver core, PCI, OF, and platform rust
bindings (all acked by the different subsystem maintainers), hence the
merge conflict with the rust tree, and some driver core api updates to
mark things as const, which will also require some fixups due to new
stuff coming in through other trees in this merge window.
There are also a bunch of debugfs updates from Al, and there is at
least one user that does have a regression with these, but Al is
working on tracking down the fix for it. In my use (and everyone
else's linux-next use), it does not seem like a big issue at the
moment.
Here's a short list of the things in here:
- driver core rust bindings for PCI, platform, OF, and some i/o
functions.
We are almost at the "write a real driver in rust" stage now,
depending on what you want to do.
- misc device rust bindings and a sample driver to show how to use
them
- debugfs cleanups in the fs as well as the users of the fs api for
places where drivers got it wrong or were unnecessarily doing
things in complex ways.
- driver core const work, making more of the api take const * for
different parameters to make the rust bindings easier overall.
- other small fixes and updates
All of these have been in linux-next with all of the aforementioned
merge conflicts, and the one debugfs issue, which looks to be resolved
"soon""
* tag 'driver-core-6.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (95 commits)
rust: device: Use as_char_ptr() to avoid explicit cast
rust: device: Replace CString with CStr in property_present()
devcoredump: Constify 'struct bin_attribute'
devcoredump: Define 'struct bin_attribute' through macro
rust: device: Add property_present()
saner replacement for debugfs_rename()
orangefs-debugfs: don't mess with ->d_name
octeontx2: don't mess with ->d_parent or ->d_parent->d_name
arm_scmi: don't mess with ->d_parent->d_name
slub: don't mess with ->d_name
sof-client-ipc-flood-test: don't mess with ->d_name
qat: don't mess with ->d_name
xhci: don't mess with ->d_iname
mtu3: don't mess wiht ->d_iname
greybus/camera - stop messing with ->d_iname
mediatek: stop messing with ->d_iname
netdevsim: don't embed file_operations into your structs
b43legacy: make use of debugfs_get_aux()
b43: stop embedding struct file_operations into their objects
carl9170: stop embedding file_operations into their objects
...
Add the const qualifier to all the ctl_tables in the tree except for
watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls,
loadpin_sysctl_table and the ones calling register_net_sysctl (./net,
drivers/inifiniband dirs). These are special cases as they use a
registration function with a non-const qualified ctl_table argument or
modify the arrays before passing them on to the registration function.
Constifying ctl_table structs will prevent the modification of
proc_handler function pointers as the arrays would reside in .rodata.
This is made possible after commit 78eb4ea25c ("sysctl: treewide:
constify the ctl_table argument of proc_handlers") constified all the
proc_handlers.
Created this by running an spatch followed by a sed command:
Spatch:
virtual patch
@
depends on !(file in "net")
disable optional_qualifier
@
identifier table_name != {
watchdog_hardlockup_sysctl,
iwcm_ctl_table,
ucma_ctl_table,
memory_allocation_profiling_sysctls,
loadpin_sysctl_table
};
@@
+ const
struct ctl_table table_name [] = { ... };
sed:
sed --in-place \
-e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \
kernel/utsname_sysctl.c
Reviewed-by: Song Liu <song@kernel.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org> # for kernel/trace/
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com> # SCSI
Reviewed-by: Darrick J. Wong <djwong@kernel.org> # xfs
Acked-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Wei Liu <wei.liu@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Acked-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Joel Granados <joel.granados@kernel.org>
Pull MM updates from Andrew Morton:
"The various patchsets are summarized below. Plus of course many
indivudual patches which are described in their changelogs.
- "Allocate and free frozen pages" from Matthew Wilcox reorganizes
the page allocator so we end up with the ability to allocate and
free zero-refcount pages. So that callers (ie, slab) can avoid a
refcount inc & dec
- "Support large folios for tmpfs" from Baolin Wang teaches tmpfs to
use large folios other than PMD-sized ones
- "Fix mm/rodata_test" from Petr Tesarik performs some maintenance
and fixes for this small built-in kernel selftest
- "mas_anode_descend() related cleanup" from Wei Yang tidies up part
of the mapletree code
- "mm: fix format issues and param types" from Keren Sun implements a
few minor code cleanups
- "simplify split calculation" from Wei Yang provides a few fixes and
a test for the mapletree code
- "mm/vma: make more mmap logic userland testable" from Lorenzo
Stoakes continues the work of moving vma-related code into the
(relatively) new mm/vma.c
- "mm/page_alloc: gfp flags cleanups for alloc_contig_*()" from David
Hildenbrand cleans up and rationalizes handling of gfp flags in the
page allocator
- "readahead: Reintroduce fix for improper RA window sizing" from Jan
Kara is a second attempt at fixing a readahead window sizing issue.
It should reduce the amount of unnecessary reading
- "synchronously scan and reclaim empty user PTE pages" from Qi Zheng
addresses an issue where "huge" amounts of pte pagetables are
accumulated:
https://lore.kernel.org/lkml/cover.1718267194.git.zhengqi.arch@bytedance.com/
Qi's series addresses this windup by synchronously freeing PTE
memory within the context of madvise(MADV_DONTNEED)
- "selftest/mm: Remove warnings found by adding compiler flags" from
Muhammad Usama Anjum fixes some build warnings in the selftests
code when optional compiler warnings are enabled
- "mm: don't use __GFP_HARDWALL when migrating remote pages" from
David Hildenbrand tightens the allocator's observance of
__GFP_HARDWALL
- "pkeys kselftests improvements" from Kevin Brodsky implements
various fixes and cleanups in the MM selftests code, mainly
pertaining to the pkeys tests
- "mm/damon: add sample modules" from SeongJae Park enhances DAMON to
estimate application working set size
- "memcg/hugetlb: Rework memcg hugetlb charging" from Joshua Hahn
provides some cleanups to memcg's hugetlb charging logic
- "mm/swap_cgroup: remove global swap cgroup lock" from Kairui Song
removes the global swap cgroup lock. A speedup of 10% for a
tmpfs-based kernel build was demonstrated
- "zram: split page type read/write handling" from Sergey Senozhatsky
has several fixes and cleaups for zram in the area of
zram_write_page(). A watchdog softlockup warning was eliminated
- "move pagetable_*_dtor() to __tlb_remove_table()" from Kevin
Brodsky cleans up the pagetable destructor implementations. A rare
use-after-free race is fixed
- "mm/debug: introduce and use VM_WARN_ON_VMG()" from Lorenzo Stoakes
simplifies and cleans up the debugging code in the VMA merging
logic
- "Account page tables at all levels" from Kevin Brodsky cleans up
and regularizes the pagetable ctor/dtor handling. This results in
improvements in accounting accuracy
- "mm/damon: replace most damon_callback usages in sysfs with new
core functions" from SeongJae Park cleans up and generalizes
DAMON's sysfs file interface logic
- "mm/damon: enable page level properties based monitoring" from
SeongJae Park increases the amount of information which is
presented in response to DAMOS actions
- "mm/damon: remove DAMON debugfs interface" from SeongJae Park
removes DAMON's long-deprecated debugfs interfaces. Thus the
migration to sysfs is completed
- "mm/hugetlb: Refactor hugetlb allocation resv accounting" from
Peter Xu cleans up and generalizes the hugetlb reservation
accounting
- "mm: alloc_pages_bulk: small API refactor" from Luiz Capitulino
removes a never-used feature of the alloc_pages_bulk() interface
- "mm/damon: extend DAMOS filters for inclusion" from SeongJae Park
extends DAMOS filters to support not only exclusion (rejecting),
but also inclusion (allowing) behavior
- "Add zpdesc memory descriptor for zswap.zpool" from Alex Shi
introduces a new memory descriptor for zswap.zpool that currently
overlaps with struct page for now. This is part of the effort to
reduce the size of struct page and to enable dynamic allocation of
memory descriptors
- "mm, swap: rework of swap allocator locks" from Kairui Song redoes
and simplifies the swap allocator locking. A speedup of 400% was
demonstrated for one workload. As was a 35% reduction for kernel
build time with swap-on-zram
- "mm: update mips to use do_mmap(), make mmap_region() internal"
from Lorenzo Stoakes reworks MIPS's use of mmap_region() so that
mmap_region() can be made MM-internal
- "mm/mglru: performance optimizations" from Yu Zhao fixes a few
MGLRU regressions and otherwise improves MGLRU performance
- "Docs/mm/damon: add tuning guide and misc updates" from SeongJae
Park updates DAMON documentation
- "Cleanup for memfd_create()" from Isaac Manjarres does that thing
- "mm: hugetlb+THP folio and migration cleanups" from David
Hildenbrand provides various cleanups in the areas of hugetlb
folios, THP folios and migration
- "Uncached buffered IO" from Jens Axboe implements the new
RWF_DONTCACHE flag which provides synchronous dropbehind for
pagecache reading and writing. To permite userspace to address
issues with massive buildup of useless pagecache when
reading/writing fast devices
- "selftests/mm: virtual_address_range: Reduce memory" from Thomas
Weißschuh fixes and optimizes some of the MM selftests"
* tag 'mm-stable-2025-01-26-14-59' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (321 commits)
mm/compaction: fix UBSAN shift-out-of-bounds warning
s390/mm: add missing ctor/dtor on page table upgrade
kasan: sw_tags: use str_on_off() helper in kasan_init_sw_tags()
tools: add VM_WARN_ON_VMG definition
mm/damon/core: use str_high_low() helper in damos_wmark_wait_us()
seqlock: add missing parameter documentation for raw_seqcount_try_begin()
mm/page-writeback: consolidate wb_thresh bumping logic into __wb_calc_thresh
mm/page_alloc: remove the incorrect and misleading comment
zram: remove zcomp_stream_put() from write_incompressible_page()
mm: separate move/undo parts from migrate_pages_batch()
mm/kfence: use str_write_read() helper in get_access_type()
selftests/mm/mkdirty: fix memory leak in test_uffdio_copy()
kasan: hw_tags: Use str_on_off() helper in kasan_init_hw_tags()
selftests/mm: virtual_address_range: avoid reading from VM_IO mappings
selftests/mm: vm_util: split up /proc/self/smaps parsing
selftests/mm: virtual_address_range: unmap chunks after validation
selftests/mm: virtual_address_range: mmap() without PROT_WRITE
selftests/memfd/memfd_test: fix possible NULL pointer dereference
mm: add FGP_DONTCACHE folio creation flag
mm: call filemap_fdatawrite_range_kick() after IOCB_DONTCACHE issue
...
Pull bpf updates from Alexei Starovoitov:
"A smaller than usual release cycle.
The main changes are:
- Prepare selftest to run with GCC-BPF backend (Ihor Solodrai)
In addition to LLVM-BPF runs the BPF CI now runs GCC-BPF in compile
only mode. Half of the tests are failing, since support for
btf_decl_tag is still WIP, but this is a great milestone.
- Convert various samples/bpf to selftests/bpf/test_progs format
(Alexis Lothoré and Bastien Curutchet)
- Teach verifier to recognize that array lookup with constant
in-range index will always succeed (Daniel Xu)
- Cleanup migrate disable scope in BPF maps (Hou Tao)
- Fix bpf_timer destroy path in PREEMPT_RT (Hou Tao)
- Always use bpf_mem_alloc in bpf_local_storage in PREEMPT_RT (Martin
KaFai Lau)
- Refactor verifier lock support (Kumar Kartikeya Dwivedi)
This is a prerequisite for upcoming resilient spin lock.
- Remove excessive 'may_goto +0' instructions in the verifier that
LLVM leaves when unrolls the loops (Yonghong Song)
- Remove unhelpful bpf_probe_write_user() warning message (Marco
Elver)
- Add fd_array_cnt attribute for prog_load command (Anton Protopopov)
This is a prerequisite for upcoming support for static_branch"
* tag 'bpf-next-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (125 commits)
selftests/bpf: Add some tests related to 'may_goto 0' insns
bpf: Remove 'may_goto 0' instruction in opt_remove_nops()
bpf: Allow 'may_goto 0' instruction in verifier
selftests/bpf: Add test case for the freeing of bpf_timer
bpf: Cancel the running bpf_timer through kworker for PREEMPT_RT
bpf: Free element after unlock in __htab_map_lookup_and_delete_elem()
bpf: Bail out early in __htab_map_lookup_and_delete_elem()
bpf: Free special fields after unlock in htab_lru_map_delete_node()
tools: Sync if_xdp.h uapi tooling header
libbpf: Work around kernel inconsistently stripping '.llvm.' suffix
bpf: selftests: verifier: Add nullness elision tests
bpf: verifier: Support eliding map lookup nullness
bpf: verifier: Refactor helper access type tracking
bpf: tcp: Mark bpf_load_hdr_opt() arg2 as read-write
bpf: verifier: Add missing newline on verbose() call
selftests/bpf: Add distilled BTF test about marking BTF_IS_EMBEDDED
libbpf: Fix incorrect traversal end type ID when marking BTF_IS_EMBEDDED
libbpf: Fix return zero when elf_begin failed
selftests/bpf: Fix btf leak on new btf alloc failure in btf_distill test
veristat: Load struct_ops programs only once
...
Since 'may_goto 0' insns are actually no-op, let us remove them.
Otherwise, verifier will generate code like
/* r10 - 8 stores the implicit loop count */
r11 = *(u64 *)(r10 -8)
if r11 == 0x0 goto pc+2
r11 -= 1
*(u64 *)(r10 -8) = r11
which is the pure overhead.
The following code patterns (from the previous commit) are also
handled:
may_goto 2
may_goto 1
may_goto 0
With this commit, the above three 'may_goto' insns are all
eliminated.
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250118192029.2124584-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Commit 011832b97b ("bpf: Introduce may_goto instruction") added support
for may_goto insn. The 'may_goto 0' insn is disallowed since the insn is
equivalent to a nop as both branch will go to the next insn.
But it is possible that compiler transformation may generate 'may_goto 0'
insn. Emil Tsalapatis from Meta reported such a case which caused
verification failure. For example, for the following code,
int i, tmp[3];
for (i = 0; i < 3 && can_loop; i++)
tmp[i] = 0;
...
clang 20 may generate code like
may_goto 2;
may_goto 1;
may_goto 0;
r1 = 0; /* tmp[0] = 0; */
r2 = 0; /* tmp[1] = 0; */
r3 = 0; /* tmp[2] = 0; */
Let us permit 'may_goto 0' insn to avoid verification failure for codes
like the above.
Reported-by: Emil Tsalapatis <etsal@meta.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20250118192024.2124059-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
During the update procedure, when overwrite element in a pre-allocated
htab, the freeing of old_element is protected by the bucket lock. The
reason why the bucket lock is necessary is that the old_element has
already been stashed in htab->extra_elems after alloc_htab_elem()
returns. If freeing the old_element after the bucket lock is unlocked,
the stashed element may be reused by concurrent update procedure and the
freeing of old_element will run concurrently with the reuse of the
old_element. However, the invocation of check_and_free_fields() may
acquire a spin-lock which violates the lockdep rule because its caller
has already held a raw-spin-lock (bucket lock). The following warning
will be reported when such race happens:
BUG: scheduling while atomic: test_progs/676/0x00000003
3 locks held by test_progs/676:
#0: ffffffff864b0240 (rcu_read_lock_trace){....}-{0:0}, at: bpf_prog_test_run_syscall+0x2c0/0x830
#1: ffff88810e961188 (&htab->lockdep_key){....}-{2:2}, at: htab_map_update_elem+0x306/0x1500
#2: ffff8881f4eac1b8 (&base->softirq_expiry_lock){....}-{2:2}, at: hrtimer_cancel_wait_running+0xe9/0x1b0
Modules linked in: bpf_testmod(O)
Preemption disabled at:
[<ffffffff817837a3>] htab_map_update_elem+0x293/0x1500
CPU: 0 UID: 0 PID: 676 Comm: test_progs Tainted: G ... 6.12.0+ #11
Tainted: [W]=WARN, [O]=OOT_MODULE
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)...
Call Trace:
<TASK>
dump_stack_lvl+0x57/0x70
dump_stack+0x10/0x20
__schedule_bug+0x120/0x170
__schedule+0x300c/0x4800
schedule_rtlock+0x37/0x60
rtlock_slowlock_locked+0x6d9/0x54c0
rt_spin_lock+0x168/0x230
hrtimer_cancel_wait_running+0xe9/0x1b0
hrtimer_cancel+0x24/0x30
bpf_timer_delete_work+0x1d/0x40
bpf_timer_cancel_and_free+0x5e/0x80
bpf_obj_free_fields+0x262/0x4a0
check_and_free_fields+0x1d0/0x280
htab_map_update_elem+0x7fc/0x1500
bpf_prog_9f90bc20768e0cb9_overwrite_cb+0x3f/0x43
bpf_prog_ea601c4649694dbd_overwrite_timer+0x5d/0x7e
bpf_prog_test_run_syscall+0x322/0x830
__sys_bpf+0x135d/0x3ca0
__x64_sys_bpf+0x75/0xb0
x64_sys_call+0x1b5/0xa10
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
...
</TASK>
It seems feasible to break the reuse and refill of per-cpu extra_elems
into two independent parts: reuse the per-cpu extra_elems with bucket
lock being held and refill the old_element as per-cpu extra_elems after
the bucket lock is unlocked. However, it will make the concurrent
overwrite procedures on the same CPU return unexpected -E2BIG error when
the map is full.
Therefore, the patch fixes the lock problem by breaking the cancelling
of bpf_timer into two steps for PREEMPT_RT:
1) use hrtimer_try_to_cancel() and check its return value
2) if the timer is running, use hrtimer_cancel() through a kworker to
cancel it again
Considering that the current implementation of hrtimer_cancel() will try
to acquire a being held softirq_expiry_lock when the current timer is
running, these steps above are reasonable. However, it also has
downside. When the timer is running, the cancelling of the timer is
delayed when releasing the last map uref. The delay is also fixable
(e.g., break the cancelling of bpf timer into two parts: one part in
locked scope, another one in unlocked scope), it can be revised later if
necessary.
It is a bit hard to decide the right fix tag. One reason is that the
problem depends on PREEMPT_RT which is enabled in v6.12. Considering the
softirq_expiry_lock lock exists since v5.4 and bpf_timer is introduced
in v5.15, the bpf_timer commit is used in the fixes tag and an extra
depends-on tag is added to state the dependency on PREEMPT_RT.
Fixes: b00628b1c7 ("bpf: Introduce bpf timers.")
Depends-on: v6.12+ with PREEMPT_RT enabled
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Closes: https://lore.kernel.org/bpf/20241106084527.4gPrMnHt@linutronix.de
Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@kernel.org>
Link: https://lore.kernel.org/r/20250117101816.2101857-5-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The freeing of special fields in map value may acquire a spin-lock
(e.g., the freeing of bpf_timer), however, the lookup_and_delete_elem
procedure has already held a raw-spin-lock, which violates the lockdep
rule.
The running context of __htab_map_lookup_and_delete_elem() has already
disabled the migration. Therefore, it is OK to invoke free_htab_elem()
after unlocking the bucket lock.
Fix the potential problem by freeing element after unlocking bucket lock
in __htab_map_lookup_and_delete_elem().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250117101816.2101857-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When bpf_timer is used in LRU hash map, calling check_and_free_fields()
in htab_lru_map_delete_node() will invoke bpf_timer_cancel_and_free() to
free the bpf_timer. If the timer is running on other CPUs,
hrtimer_cancel() will invoke hrtimer_cancel_wait_running() to spin on
current CPU to wait for the completion of the hrtimer callback.
Considering that the deletion has already acquired a raw-spin-lock
(bucket lock). To reduce the time holding the bucket lock, move the
invocation of check_and_free_fields() out of bucket lock. However,
because htab_lru_map_delete_node() is invoked with LRU raw spin lock
being held, the freeing of special fields still happens in a locked
scope.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@kernel.org>
Link: https://lore.kernel.org/r/20250117101816.2101857-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit allows progs to elide a null check on statically known map
lookup keys. In other words, if the verifier can statically prove that
the lookup will be in-bounds, allow the prog to drop the null check.
This is useful for two reasons:
1. Large numbers of nullness checks (especially when they cannot fail)
unnecessarily pushes prog towards BPF_COMPLEXITY_LIMIT_JMP_SEQ.
2. It forms a tighter contract between programmer and verifier.
For (1), bpftrace is starting to make heavier use of percpu scratch
maps. As a result, for user scripts with large number of unrolled loops,
we are starting to hit jump complexity verification errors. These
percpu lookups cannot fail anyways, as we only use static key values.
Eliding nullness probably results in less work for verifier as well.
For (2), percpu scratch maps are often used as a larger stack, as the
currrent stack is limited to 512 bytes. In these situations, it is
desirable for the programmer to express: "this lookup should never fail,
and if it does, it means I messed up the code". By omitting the null
check, the programmer can "ask" the verifier to double check the logic.
Tests also have to be updated in sync with these changes, as the
verifier is more efficient with this change. Notable, iters.c tests had
to be changed to use a map type that still requires null checks, as it's
exercising verifier tracking logic w.r.t iterators.
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/68f3ea96ff3809a87e502a11a4bd30177fc5823e.1736886479.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Previously, the verifier was treating all PTR_TO_STACK registers passed
to a helper call as potentially written to by the helper. However, all
calls to check_stack_range_initialized() already have precise access type
information available.
Rather than treat ACCESS_HELPER as a proxy for BPF_WRITE, pass
enum bpf_access_type to check_stack_range_initialized() to more
precisely track helper arguments.
One benefit from this precision is that registers tracked as valid
spills and passed as a read-only helper argument remain tracked after
the call. Rather than being marked STACK_MISC afterwards.
An additional benefit is the verifier logs are also more precise. For
this particular error, users will enjoy a slightly clearer message. See
included selftest updates for examples.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Link: https://lore.kernel.org/r/ff885c0e5859e0cd12077c3148ff0754cad4f7ed.1736886479.git.dxu@dxuuu.xyz
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
We need the debugfs / driver-core fixes in here as well for testing and
to build on top of.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf_selem_free() has the following three callers:
(1) bpf_local_storage_update
It will be invoked through ->map_update_elem syscall or helpers for
storage map. Migration has already been disabled in these running
contexts.
(2) bpf_sk_storage_clone
It has already disabled migration before invoking bpf_selem_free().
(3) bpf_selem_free_list
bpf_selem_free_list() has three callers: bpf_selem_unlink_storage(),
bpf_local_storage_update() and bpf_local_storage_destroy().
The callers of bpf_selem_unlink_storage() includes: storage map
->map_delete_elem syscall, storage map delete helpers and
bpf_local_storage_map_free(). These contexts have already disabled
migration when invoking bpf_selem_unlink() which invokes
bpf_selem_unlink_storage() and bpf_selem_free_list() correspondingly.
bpf_local_storage_update() has been analyzed as the first caller above.
bpf_local_storage_destroy() is invoked when freeing the local storage
for the kernel object. Now cgroup, task, inode and sock storage have
already disabled migration before invoking bpf_local_storage_destroy().
After the analyses above, it is safe to remove migrate_{disable|enable}
from bpf_selem_free().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-17-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_local_storage_free() has three callers:
1) bpf_local_storage_alloc()
Its caller must have disabled migration.
2) bpf_local_storage_destroy()
Its four callers (bpf_{cgrp|inode|task|sk}_storage_free()) have already
invoked migrate_disable() before invoking bpf_local_storage_destroy().
3) bpf_selem_unlink()
Its callers include: cgrp/inode/task/sk storage ->map_delete_elem
callbacks, bpf_{cgrp|inode|task|sk}_storage_delete() helpers and
bpf_local_storage_map_free(). All of these callers have already disabled
migration before invoking bpf_selem_unlink().
Therefore, it is OK to remove migrate_{disable|enable} pair from
bpf_local_storage_free().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-16-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
These two callers of bpf_local_storage_alloc() are the same as
bpf_selem_alloc(): bpf_sk_storage_clone() and
bpf_local_storage_update(). The running contexts of these two callers
have already disabled migration, therefore, there is no need to add
extra migrate_{disable|enable} pair in bpf_local_storage_alloc().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-15-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_selem_alloc() has two callers:
(1) bpf_sk_storage_clone_elem()
bpf_sk_storage_clone() has already disabled migration before invoking
bpf_sk_storage_clone_elem().
(2) bpf_local_storage_update()
Its callers include: cgrp/task/inode/sock storage ->map_update_elem()
callbacks and bpf_{cgrp|task|inode|sk}_storage_get() helpers. These
running contexts have already disabled migration
Therefore, there is no need to add extra migrate_{disable|enable} pair
in bpf_selem_alloc().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-14-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When BPF program invokes bpf_cpumask_release(), the migration must have
been disabled. When bpf_cpumask_release_dtor() invokes
bpf_cpumask_release(), the caller bpf_obj_free_fields() also has
disabled migration, therefore, it is OK to remove the unnecessary
migrate_{disable|enable} pair in bpf_cpumask_release().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-13-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The callers of bpf_obj_free_fields() have already guaranteed that the
migration is disabled, therefore, there is no need to invoke
migrate_{disable,enable} pair in bpf_obj_free_fields()'s underly
implementation.
This patch removes unnecessary migrate_{disable|enable} pairs from
bpf_obj_free_fields() and its callees: bpf_list_head_free() and
bpf_rb_root_free().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-12-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
The freeing of all map elements may invoke bpf_obj_free_fields() to free
the special fields in the map value. Since these special fields may be
allocated from bpf memory allocator, migrate_{disable|enable} pairs are
necessary for the freeing of these special fields.
To simplify reasoning about when migrate_disable() is needed for the
freeing of these special fields, let the caller to guarantee migration
is disabled before invoking bpf_obj_free_fields(). Therefore, disabling
migration before calling ops->map_free() to simplify the freeing of map
values or special fields allocated from bpf memory allocator.
After disabling migration in bpf_map_free(), there is no need for
additional migration_{disable|enable} pairs in these ->map_free()
callbacks. Remove these redundant invocations.
The migrate_{disable|enable} pairs in the underlying implementation of
bpf_obj_free_fields() will be removed by the following patch.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-11-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
bpf_selem_free_rcu() calls bpf_obj_free_fields() to free the special
fields in map value (e.g., kptr). Since kptrs may be allocated from bpf
memory allocator, migrate_{disable|enable} pairs are necessary for the
freeing of these kptrs.
To simplify reasoning about when migrate_disable() is needed for the
freeing of these dynamically-allocated kptrs, let the caller to
guarantee migration is disabled before invoking bpf_obj_free_fields().
Therefore, the patch adds migrate_{disable|enable} pair in
bpf_selem_free_rcu(). The migrate_{disable|enable} pairs in the
underlying implementation of bpf_obj_free_fields() will be removed by
the following patch.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-10-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When destroying inode storage, it invokes bpf_local_storage_destroy() to
remove all storage elements saved in the inode storage. The destroy
procedure will call bpf_selem_free() to free the element, and
bpf_selem_free() calls bpf_obj_free_fields() to free the special fields
in map value (e.g., kptr). Since kptrs may be allocated from bpf memory
allocator, migrate_{disable|enable} pairs are necessary for the freeing
of these kptrs.
To simplify reasoning about when migrate_disable() is needed for the
freeing of these dynamically-allocated kptrs, let the caller to
guarantee migration is disabled before invoking bpf_obj_free_fields().
Therefore, the patch adds migrate_{disable|enable} pair in
bpf_inode_storage_free(). The migrate_{disable|enable} pairs in the
underlying implementation of bpf_obj_free_fields() will be removed by
the following patch.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-7-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Three callers of bpf_task_storage_lock() are ->map_lookup_elem,
->map_update_elem, ->map_delete_elem from bpf syscall. BPF syscall for
these three operations of task storage has already disabled migration.
Another two callers are bpf_task_storage_get() and
bpf_task_storage_delete() helpers which will be used by BPF program.
Two callers of bpf_task_storage_trylock() are bpf_task_storage_get() and
bpf_task_storage_delete() helpers. The running contexts of these helpers
have already disabled migration.
Therefore, it is safe to remove migrate_{disable|enable} from task
storage lock helpers for these call sites. However,
bpf_task_storage_free() also invokes bpf_task_storage_lock() and its
running context doesn't disable migration, therefore, add the missed
migrate_{disable|enable} in bpf_task_storage_free().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-6-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Three callers of bpf_cgrp_storage_lock() are ->map_lookup_elem,
->map_update_elem, ->map_delete_elem from bpf syscall. BPF syscall for
these three operations of cgrp storage has already disabled migration.
Two call sites of bpf_cgrp_storage_trylock() are bpf_cgrp_storage_get(),
and bpf_cgrp_storage_delete() helpers. The running contexts of these
helpers have already disabled migration.
Therefore, it is safe to remove migrate_disable() for these callers.
However, bpf_cgrp_storage_free() also invokes bpf_cgrp_storage_lock()
and its running context doesn't disable migration. Therefore, also add
the missed migrate_{disabled|enable} in bpf_cgrp_storage_free().
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-5-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
htab_elem_free() has two call-sites: delete_all_elements() has already
disabled migration, free_htab_elem() is invoked by other 4 functions:
__htab_map_lookup_and_delete_elem, __htab_map_lookup_and_delete_batch,
htab_map_update_elem and htab_map_delete_elem.
BPF syscall has already disabled migration before invoking
->map_update_elem, ->map_delete_elem, and ->map_lookup_and_delete_elem
callbacks for hash map. __htab_map_lookup_and_delete_batch() also
disables migration before invoking free_htab_elem(). ->map_update_elem()
and ->map_delete_elem() of hash map may be invoked by BPF program and
the running context of BPF program has already disabled migration.
Therefore, it is safe to remove the migration_{disable|enable} pair in
htab_elem_free()
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
BPF program may call bpf_for_each_map_elem(), and it will call
the ->map_for_each_callback callback of related bpf map. Considering the
running context of bpf program has already disabled migration, remove
the unnecessary migrate_{disable|enable} pair in the implementations of
->map_for_each_callback. To ensure the guarantee will not be voilated
later, also add cant_migrate() check in the implementations.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Both bpf program and bpf syscall may invoke ->update or ->delete
operation for LPM trie. For bpf program, its running context has already
disabled migration explicitly through (migrate_disable()) or implicitly
through (preempt_disable() or disable irq). For bpf syscall, the
migration is disabled through the use of bpf_disable_instrumentation()
before invoking the corresponding map operation callback.
Therefore, it is safe to remove the migrate_{disable|enable){} pair from
LPM trie.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-2-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
There is a UAF report in the bpf_struct_ops when CONFIG_MODULES=n.
In particular, the report is on tcp_congestion_ops that has
a "struct module *owner" member.
For struct_ops that has a "struct module *owner" member,
it can be extended either by the regular kernel module or
by the bpf_struct_ops. bpf_try_module_get() will be used
to do the refcounting and different refcount is done
based on the owner pointer. When CONFIG_MODULES=n,
the btf_id of the "struct module" is missing:
WARN: resolve_btfids: unresolved symbol module
Thus, the bpf_try_module_get() cannot do the correct refcounting.
Not all subsystem's struct_ops requires the "struct module *owner" member.
e.g. the recent sched_ext_ops.
This patch is to disable bpf_struct_ops registration if
the struct_ops has the "struct module *" member and the
"struct module" btf_id is missing. The btf_type_is_fwd() helper
is moved to the btf.h header file for this test.
This has happened since the beginning of bpf_struct_ops which has gone
through many changes. The Fixes tag is set to a recent commit that this
patch can apply cleanly. Considering CONFIG_MODULES=n is not
common and the age of the issue, targeting for bpf-next also.
Fixes: 1611603537 ("bpf: Create argument information for nullable arguments.")
Reported-by: Robert Morris <rtm@csail.mit.edu>
Closes: https://lore.kernel.org/bpf/74665.1733669976@localhost/
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Tested-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20241220201818.127152-1-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch improves (or maintains) the precision of register value tracking
in BPF_MUL across all possible inputs. It also simplifies
scalar32_min_max_mul() and scalar_min_max_mul().
As it stands, BPF_MUL is composed of three functions:
case BPF_MUL:
tnum_mul();
scalar32_min_max_mul();
scalar_min_max_mul();
The current implementation of scalar_min_max_mul() restricts the u64 input
ranges of dst_reg and src_reg to be within [0, U32_MAX]:
/* Both values are positive, so we can work with unsigned and
* copy the result to signed (unless it exceeds S64_MAX).
*/
if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) {
/* Potential overflow, we know nothing */
__mark_reg64_unbounded(dst_reg);
return;
}
This restriction is done to avoid unsigned overflow, which could otherwise
wrap the result around 0, and leave an unsound output where umin > umax. We
also observe that limiting these u64 input ranges to [0, U32_MAX] leads to
a loss of precision. Consider the case where the u64 bounds of dst_reg are
[0, 2^34] and the u64 bounds of src_reg are [0, 2^2]. While the
multiplication of these two bounds doesn't overflow and is sound [0, 2^36],
the current scalar_min_max_mul() would set the entire register state to
unbounded.
Importantly, we update BPF_MUL to allow signed bound multiplication
(i.e. multiplying negative bounds) as well as allow u64 inputs to take on
values from [0, U64_MAX]. We perform signed multiplication on two bounds
[a,b] and [c,d] by multiplying every combination of the bounds
(i.e. a*c, a*d, b*c, and b*d) and checking for overflow of each product. If
there is an overflow, we mark the signed bounds unbounded [S64_MIN, S64_MAX].
In the case of no overflow, we take the minimum of these products to
be the resulting smin, and the maximum to be the resulting smax.
The key idea here is that if there’s no possibility of overflow, either
when multiplying signed bounds or unsigned bounds, we can safely multiply the
respective bounds; otherwise, we set the bounds that exhibit overflow
(during multiplication) to unbounded.
if (check_mul_overflow(*dst_umax, src_reg->umax_value, dst_umax) ||
(check_mul_overflow(*dst_umin, src_reg->umin_value, dst_umin))) {
/* Overflow possible, we know nothing */
*dst_umin = 0;
*dst_umax = U64_MAX;
}
...
Below, we provide an example BPF program (below) that exhibits the
imprecision in the current BPF_MUL, where the outputs are all unbounded. In
contrast, the updated BPF_MUL produces a bounded register state:
BPF_LD_IMM64(BPF_REG_1, 11),
BPF_LD_IMM64(BPF_REG_2, 4503599627370624),
BPF_ALU64_IMM(BPF_NEG, BPF_REG_2, 0),
BPF_ALU64_IMM(BPF_NEG, BPF_REG_2, 0),
BPF_ALU64_REG(BPF_AND, BPF_REG_1, BPF_REG_2),
BPF_LD_IMM64(BPF_REG_3, 809591906117232263),
BPF_ALU64_REG(BPF_MUL, BPF_REG_3, BPF_REG_1),
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_EXIT_INSN(),
Verifier log using the old BPF_MUL:
func#0 @0
0: R1=ctx() R10=fp0
0: (18) r1 = 0xb ; R1_w=11
2: (18) r2 = 0x10000000000080 ; R2_w=0x10000000000080
4: (87) r2 = -r2 ; R2_w=scalar()
5: (87) r2 = -r2 ; R2_w=scalar()
6: (5f) r1 &= r2 ; R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=11,var_off=(0x0; 0xb)) R2_w=scalar()
7: (18) r3 = 0xb3c3f8c99262687 ; R3_w=0xb3c3f8c99262687
9: (2f) r3 *= r1 ; R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=11,var_off=(0x0; 0xb)) R3_w=scalar()
...
Verifier using the new updated BPF_MUL (more precise bounds at label 9)
func#0 @0
0: R1=ctx() R10=fp0
0: (18) r1 = 0xb ; R1_w=11
2: (18) r2 = 0x10000000000080 ; R2_w=0x10000000000080
4: (87) r2 = -r2 ; R2_w=scalar()
5: (87) r2 = -r2 ; R2_w=scalar()
6: (5f) r1 &= r2 ; R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=11,var_off=(0x0; 0xb)) R2_w=scalar()
7: (18) r3 = 0xb3c3f8c99262687 ; R3_w=0xb3c3f8c99262687
9: (2f) r3 *= r1 ; R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=11,var_off=(0x0; 0xb)) R3_w=scalar(smin=0,smax=umax=0x7b96bb0a94a3a7cd,var_off=(0x0; 0x7fffffffffffffff))
...
Finally, we proved the soundness of the new scalar_min_max_mul() and
scalar32_min_max_mul() functions. Typically, multiplication operations are
expensive to check with bitvector-based solvers. We were able to prove the
soundness of these functions using Non-Linear Integer Arithmetic (NIA)
theory. Additionally, using Agni [2,3], we obtained the encodings for
scalar32_min_max_mul() and scalar_min_max_mul() in bitvector theory, and
were able to prove their soundness using 8-bit bitvectors (instead of
64-bit bitvectors that the functions actually use).
In conclusion, with this patch,
1. We were able to show that we can improve the overall precision of
BPF_MUL. We proved (using an SMT solver) that this new version of
BPF_MUL is at least as precise as the current version for all inputs
and more precise for some inputs.
2. We are able to prove the soundness of the new scalar_min_max_mul() and
scalar32_min_max_mul(). By leveraging the existing proof of tnum_mul
[1], we can say that the composition of these three functions within
BPF_MUL is sound.
[1] https://ieeexplore.ieee.org/abstract/document/9741267
[2] https://link.springer.com/chapter/10.1007/978-3-031-37709-9_12
[3] https://people.cs.rutgers.edu/~sn349/papers/sas24-preprint.pdf
Co-developed-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Signed-off-by: Harishankar Vishwanathan <harishankar.vishwanathan@gmail.com>
Co-developed-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Signed-off-by: Srinivas Narayana <srinivas.narayana@rutgers.edu>
Co-developed-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Santosh Nagarakatte <santosh.nagarakatte@rutgers.edu>
Signed-off-by: Matan Shachnai <m.shachnai@gmail.com>
Link: https://lore.kernel.org/r/20241218032337.12214-2-m.shachnai@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In PREEMPT_RT, kmalloc(GFP_ATOMIC) is still not safe in non preemptible
context. bpf_mem_alloc must be used in PREEMPT_RT. This patch is
to enforce bpf_mem_alloc in the bpf_local_storage when CONFIG_PREEMPT_RT
is enabled.
[ 35.118559] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
[ 35.118566] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1832, name: test_progs
[ 35.118569] preempt_count: 1, expected: 0
[ 35.118571] RCU nest depth: 1, expected: 1
[ 35.118577] INFO: lockdep is turned off.
...
[ 35.118647] __might_resched+0x433/0x5b0
[ 35.118677] rt_spin_lock+0xc3/0x290
[ 35.118700] ___slab_alloc+0x72/0xc40
[ 35.118723] __kmalloc_noprof+0x13f/0x4e0
[ 35.118732] bpf_map_kzalloc+0xe5/0x220
[ 35.118740] bpf_selem_alloc+0x1d2/0x7b0
[ 35.118755] bpf_local_storage_update+0x2fa/0x8b0
[ 35.118784] bpf_sk_storage_get_tracing+0x15a/0x1d0
[ 35.118791] bpf_prog_9a118d86fca78ebb_trace_inet_sock_set_state+0x44/0x66
[ 35.118795] bpf_trace_run3+0x222/0x400
[ 35.118820] __bpf_trace_inet_sock_set_state+0x11/0x20
[ 35.118824] trace_inet_sock_set_state+0x112/0x130
[ 35.118830] inet_sk_state_store+0x41/0x90
[ 35.118836] tcp_set_state+0x3b3/0x640
There is no need to adjust the gfp_flags passing to the
bpf_mem_cache_alloc_flags() which only honors the GFP_KERNEL.
The verifier has ensured GFP_KERNEL is passed only in sleepable context.
It has been an old issue since the first introduction of the
bpf_local_storage ~5 years ago, so this patch targets the bpf-next.
bpf_mem_alloc is needed to solve it, so the Fixes tag is set
to the commit when bpf_mem_alloc was first used in the bpf_local_storage.
Fixes: 08a7ce384e ("bpf: Use bpf_mem_cache_alloc/free in bpf_local_storage_elem")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20241218193000.2084281-1-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
On x86-64 calling bpf_get_smp_processor_id() in a kernel with CONFIG_SMP
disabled can trigger the following bug, as pcpu_hot is unavailable:
[ 8.471774] BUG: unable to handle page fault for address: 00000000936a290c
[ 8.471849] #PF: supervisor read access in kernel mode
[ 8.471881] #PF: error_code(0x0000) - not-present page
Fix by inlining a return 0 in the !CONFIG_SMP case.
Fixes: 1ae6921009 ("bpf: inline bpf_get_smp_processor_id() helper")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241217195813.622568-1-arighi@nvidia.com
Arguments to a raw tracepoint are tagged as trusted, which carries the
semantics that the pointer will be non-NULL. However, in certain cases,
a raw tracepoint argument may end up being NULL. More context about this
issue is available in [0].
Thus, there is a discrepancy between the reality, that raw_tp arguments can
actually be NULL, and the verifier's knowledge, that they are never NULL,
causing explicit NULL check branch to be dead code eliminated.
A previous attempt [1], i.e. the second fixed commit, was made to
simulate symbolic execution as if in most accesses, the argument is a
non-NULL raw_tp, except for conditional jumps. This tried to suppress
branch prediction while preserving compatibility, but surfaced issues
with production programs that were difficult to solve without increasing
verifier complexity. A more complete discussion of issues and fixes is
available at [2].
Fix this by maintaining an explicit list of tracepoints where the
arguments are known to be NULL, and mark the positional arguments as
PTR_MAYBE_NULL. Additionally, capture the tracepoints where arguments
are known to be ERR_PTR, and mark these arguments as scalar values to
prevent potential dereference.
Each hex digit is used to encode NULL-ness (0x1) or ERR_PTR-ness (0x2),
shifted by the zero-indexed argument number x 4. This can be represented
as follows:
1st arg: 0x1
2nd arg: 0x10
3rd arg: 0x100
... and so on (likewise for ERR_PTR case).
In the future, an automated pass will be used to produce such a list, or
insert __nullable annotations automatically for tracepoints. Each
compilation unit will be analyzed and results will be collated to find
whether a tracepoint pointer is definitely not null, maybe null, or an
unknown state where verifier conservatively marks it PTR_MAYBE_NULL.
A proof of concept of this tool from Eduard is available at [3].
Note that in case we don't find a specification in the raw_tp_null_args
array and the tracepoint belongs to a kernel module, we will
conservatively mark the arguments as PTR_MAYBE_NULL. This is because
unlike for in-tree modules, out-of-tree module tracepoints may pass NULL
freely to the tracepoint. We don't protect against such tracepoints
passing ERR_PTR (which is uncommon anyway), lest we mark all such
arguments as SCALAR_VALUE.
While we are it, let's adjust the test raw_tp_null to not perform
dereference of the skb->mark, as that won't be allowed anymore, and make
it more robust by using inline assembly to test the dead code
elimination behavior, which should still stay the same.
[0]: https://lore.kernel.org/bpf/ZrCZS6nisraEqehw@jlelli-thinkpadt14gen4.remote.csb
[1]: https://lore.kernel.org/all/20241104171959.2938862-1-memxor@gmail.com
[2]: https://lore.kernel.org/bpf/20241206161053.809580-1-memxor@gmail.com
[3]: https://github.com/eddyz87/llvm-project/tree/nullness-for-tracepoint-params
Reported-by: Juri Lelli <juri.lelli@redhat.com> # original bug
Reported-by: Manu Bretelle <chantra@meta.com> # bugs in masking fix
Fixes: 3f00c52393 ("bpf: Allow trusted pointers to be passed to KF_TRUSTED_ARGS kfuncs")
Fixes: cb4158ce8e ("bpf: Mark raw_tp arguments with PTR_MAYBE_NULL")
Reviewed-by: Eduard Zingerman <eddyz87@gmail.com>
Co-developed-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241213221929.3495062-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This patch reverts commit
cb4158ce8e ("bpf: Mark raw_tp arguments with PTR_MAYBE_NULL"). The
patch was well-intended and meant to be as a stop-gap fixing branch
prediction when the pointer may actually be NULL at runtime. Eventually,
it was supposed to be replaced by an automated script or compiler pass
detecting possibly NULL arguments and marking them accordingly.
However, it caused two main issues observed for production programs and
failed to preserve backwards compatibility. First, programs relied on
the verifier not exploring == NULL branch when pointer is not NULL, thus
they started failing with a 'dereference of scalar' error. Next,
allowing raw_tp arguments to be modified surfaced the warning in the
verifier that warns against reg->off when PTR_MAYBE_NULL is set.
More information, context, and discusson on both problems is available
in [0]. Overall, this approach had several shortcomings, and the fixes
would further complicate the verifier's logic, and the entire masking
scheme would have to be removed eventually anyway.
Hence, revert the patch in preparation of a better fix avoiding these
issues to replace this commit.
[0]: https://lore.kernel.org/bpf/20241206161053.809580-1-memxor@gmail.com
Reported-by: Manu Bretelle <chantra@meta.com>
Fixes: cb4158ce8e ("bpf: Mark raw_tp arguments with PTR_MAYBE_NULL")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241213221929.3495062-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
These BTF functions are not available unconditionally,
only reference them when they are available.
Avoid the following build warnings:
BTF .tmp_vmlinux1.btf.o
btf_encoder__tag_kfunc: failed to find kfunc 'bpf_send_signal_task' in BTF
btf_encoder__tag_kfuncs: failed to tag kfunc 'bpf_send_signal_task'
NM .tmp_vmlinux1.syms
KSYMS .tmp_vmlinux1.kallsyms.S
AS .tmp_vmlinux1.kallsyms.o
LD .tmp_vmlinux2
NM .tmp_vmlinux2.syms
KSYMS .tmp_vmlinux2.kallsyms.S
AS .tmp_vmlinux2.kallsyms.o
LD vmlinux
BTFIDS vmlinux
WARN: resolve_btfids: unresolved symbol prog_test_ref_kfunc
WARN: resolve_btfids: unresolved symbol bpf_crypto_ctx
WARN: resolve_btfids: unresolved symbol bpf_send_signal_task
WARN: resolve_btfids: unresolved symbol bpf_modify_return_test_tp
WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_xdp
WARN: resolve_btfids: unresolved symbol bpf_dynptr_from_skb
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241213-bpf-cond-ids-v1-1-881849997219@weissschuh.net
The fd_array attribute of the BPF_PROG_LOAD syscall may contain a set
of file descriptors: maps or btfs. This field was introduced as a
sparse array. Introduce a new attribute, fd_array_cnt, which, if
present, indicates that the fd_array is a continuous array of the
corresponding length.
If fd_array_cnt is non-zero, then every map in the fd_array will be
bound to the program, as if it was used by the program. This
functionality is similar to the BPF_PROG_BIND_MAP syscall, but such
maps can be used by the verifier during the program load.
Signed-off-by: Anton Protopopov <aspsk@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241213130934.1087929-5-aspsk@isovalent.com
