linux-stable.git/kernel/bpf/stackmap.c, branch v6.18.51

bpf: Disable preemption in bpf_get_stackid

2026-09-11T09:49:39+00:00

[ Upstream commit 15f1bd8574662f1b7b26aaa2e23ebf4066f0117d ]

The get_perf_callchain call needs disabled preemption plus we need
it disabled as long as we access its returned trace entries buffer.

Note the bpf_get_stackid_pe function is executed already with
preemption disabled.

Fixes: d5a3b1f69186 ("bpf: introduce BPF_MAP_TYPE_STACK_TRACE")
Reported-by: Tao Chen 
Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/bpf/20260803210149.296496-6-jolsa@kernel.org

Closes: https://lore.kernel.org/bpf/20260206090653.1336687-2-chen.dylane@linux.dev/
[ adapted get_perf_callchain() to the older six-argument form ]
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: Use stack id functions instead of __bpf_get_stackid

2026-09-11T09:49:39+00:00

[ Upstream commit 09b3fd6caa0b57f8a39254ee5db3af30bdd53c18 ]

Replacing __bpf_get_stackid calls with sequence of following functions:

  stackid_fastpath
  stackid_new_bucket
  stackid_install

This makes code more structured and allows us to easily disable
preemption only in bpf_get_stackid in following changes.

Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260803210149.296496-5-jolsa@kernel.org
Stable-dep-of: 15f1bd857466 ("bpf: Disable preemption in bpf_get_stackid")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: Factor stackid_new_bucket from __bpf_get_stackid

2026-09-11T09:49:39+00:00

[ Upstream commit bb4e6f4e1b68fe60c04ca04c564c6624e837dbf4 ]

The new stackid_new_bucket allocates the new bucket and initializes it
with the trace data.

Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260803210149.296496-4-jolsa@kernel.org
Stable-dep-of: 15f1bd857466 ("bpf: Disable preemption in bpf_get_stackid")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: Factor stackid_fastpath function from __bpf_get_stackid

2026-09-11T09:49:39+00:00

[ Upstream commit 0ca56befcffec3a6c9d1842eae06c74e1cf41f11 ]

The new stackid_fastpath does the fast stack hash and trace check, that
does not need new bucket allocation. It covers both just-ip and buildid
code paths.

Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260803210149.296496-3-jolsa@kernel.org
Stable-dep-of: 15f1bd857466 ("bpf: Disable preemption in bpf_get_stackid")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: Factor stackid_init function from __bpf_get_stackid

2026-09-11T09:49:38+00:00

[ Upstream commit 15b837759a97237d647962f9943afe0d55af615a ]

The new stackid_init function stores all the necessary bits for stackid
trace and it will be used by other functions in following changes.

Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20260803210149.296496-2-jolsa@kernel.org
Stable-dep-of: 15f1bd857466 ("bpf: Disable preemption in bpf_get_stackid")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

bpf: Disable preemption in __bpf_get_stack

2026-09-07T15:22:36+00:00

commit b1a47b2708d4e95dbd23aee2ec83752190897b3f upstream.

get_perf_callchain() returns a per-CPU perf_callchain_entry buffer and
releases its recursion slot via put_callchain_entry() before returning,
so nothing keeps the entry reserved while __bpf_get_stack() consumes
it below.

A preemptible BPF program (e.g. a non-sleepable raw tracepoint program
on a PREEMPT kernel, which runs under migrate_disable() but not
preempt_disable()) can be scheduled out between obtaining the entry
and the copy. Another task scheduled on the same CPU then reuses the
same per-CPU buffer and overwrites trace->nr with a larger value.
copy_len is then computed from the inflated trace->nr and can exceed
the caller's buffer, causing an out-of-bounds write in the memcpy()
and in the build_id path.

The rcu_read_lock() taken here alone does not prevent this. It is
only taken on the may_fault path, and under CONFIG_PREEMPT_RCU it does
not disable preemption; it merely keeps perf's callchain buffer array
alive (freed via call_rcu()) and does nothing to stop another task
from reusing the entry.

Disable preemption around obtaining the callchain entry and copying
it into the caller's buffer, so the entry cannot be reused underneath
us and trace->nr stays bounded by max_depth. Build ID resolution may
fault and is therefore deferred until after preemption is re-enabled;
by then the instruction pointers have already been copied into buf,
so it operates only on that private copy. Note, preempt_disable() also
subsumes the buffer-lifetime guarantee the rcu_read_lock() provided,
since a preempt-disabled section is an RCU read-side critical section
for the callchain buffers' call_rcu() reclaim.

Fixes: c195651e565a ("bpf: add bpf_get_stack helper")
Reported-by: Tao Chen 
Reported-by: STAR Labs SG 
Signed-off-by: Daniel Borkmann 
Signed-off-by: Jiri Olsa 
Signed-off-by: Andrii Nakryiko 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/bpf/20260803210149.296496-11-jolsa@kernel.org
Signed-off-by: Greg Kroah-Hartman 

Closes: https://lore.kernel.org/bpf/20260206090653.1336687-1-chen.dylane@linux.dev/
[ changed Fixes: commit ]

bpf: Fix stackmap overflow check in __bpf_get_stackid()

2025-12-18T13:02:42+00:00

[ Upstream commit 23f852daa4bab4d579110e034e4d513f7d490846 ]

Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stackid()
when copying stack trace data. The issue occurs when the perf trace
 contains more stack entries than the stack map bucket can hold,
 leading to an out-of-bounds write in the bucket's data array.

Fixes: ee2a098851bf ("bpf: Adjust BPF stack helper functions to accommodate skip > 0")
Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com
Signed-off-by: Arnaud Lecomte 
Signed-off-by: Andrii Nakryiko 
Acked-by: Yonghong Song 
Acked-by: Song Liu 
Link: https://lore.kernel.org/bpf/20251025192941.1500-1-contact@arnaud-lcm.com

Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
Signed-off-by: Sasha Levin

bpf: Refactor stack map trace depth calculation into helper function

2025-12-18T13:02:42+00:00

[ Upstream commit e17d62fedd10ae56e2426858bd0757da544dbc73 ]

Extract the duplicated maximum allowed depth computation for stack
traces stored in BPF stacks from bpf_get_stackid() and __bpf_get_stack()
into a dedicated stack_map_calculate_max_depth() helper function.

This unifies the logic for:
- The max depth computation
- Enforcing the sysctl_perf_event_max_stack limit

No functional changes for existing code paths.

Signed-off-by: Arnaud Lecomte 
Signed-off-by: Andrii Nakryiko 
Acked-by: Yonghong Song 
Acked-by: Song Liu 
Link: https://lore.kernel.org/bpf/20251025192858.31424-1-contact@arnaud-lcm.com
Stable-dep-of: 23f852daa4ba ("bpf: Fix stackmap overflow check in __bpf_get_stackid()")
Signed-off-by: Sasha Levin

Merge tag 'bpf-next-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2025-10-01T00:58:11+00:00

Pull bpf updates from Alexei Starovoitov:

 - Support pulling non-linear xdp data with bpf_xdp_pull_data() kfunc
   (Amery Hung)

   Applied as a stable branch in bpf-next and net-next trees.

 - Support reading skb metadata via bpf_dynptr (Jakub Sitnicki)

   Also a stable branch in bpf-next and net-next trees.

 - Enforce expected_attach_type for tailcall compatibility (Daniel
   Borkmann)

 - Replace path-sensitive with path-insensitive live stack analysis in
   the verifier (Eduard Zingerman)

   This is a significant change in the verification logic. More details,
   motivation, long term plans are in the cover letter/merge commit.

 - Support signed BPF programs (KP Singh)

   This is another major feature that took years to materialize.

   Algorithm details are in the cover letter/marge commit

 - Add support for may_goto instruction to s390 JIT (Ilya Leoshkevich)

 - Add support for may_goto instruction to arm64 JIT (Puranjay Mohan)

 - Fix USDT SIB argument handling in libbpf (Jiawei Zhao)

 - Allow uprobe-bpf program to change context registers (Jiri Olsa)

 - Support signed loads from BPF arena (Kumar Kartikeya Dwivedi and
   Puranjay Mohan)

 - Allow access to union arguments in tracing programs (Leon Hwang)

 - Optimize rcu_read_lock() + migrate_disable() combination where it's
   used in BPF subsystem (Menglong Dong)

 - Introduce bpf_task_work_schedule*() kfuncs to schedule deferred
   execution of BPF callback in the context of a specific task using the
   kernel’s task_work infrastructure (Mykyta Yatsenko)

 - Enforce RCU protection for KF_RCU_PROTECTED kfuncs (Kumar Kartikeya
   Dwivedi)

 - Add stress test for rqspinlock in NMI (Kumar Kartikeya Dwivedi)

 - Improve the precision of tnum multiplier verifier operation
   (Nandakumar Edamana)

 - Use tnums to improve is_branch_taken() logic (Paul Chaignon)

 - Add support for atomic operations in arena in riscv JIT (Pu Lehui)

 - Report arena faults to BPF error stream (Puranjay Mohan)

 - Search for tracefs at /sys/kernel/tracing first in bpftool (Quentin
   Monnet)

 - Add bpf_strcasecmp() kfunc (Rong Tao)

 - Support lookup_and_delete_elem command in BPF_MAP_STACK_TRACE (Tao
   Chen)

* tag 'bpf-next-6.18' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (197 commits)
  libbpf: Replace AF_ALG with open coded SHA-256
  selftests/bpf: Add stress test for rqspinlock in NMI
  selftests/bpf: Add test case for different expected_attach_type
  bpf: Enforce expected_attach_type for tailcall compatibility
  bpftool: Remove duplicate string.h header
  bpf: Remove duplicate crypto/sha2.h header
  libbpf: Fix error when st-prefix_ops and ops from differ btf
  selftests/bpf: Test changing packet data from kfunc
  selftests/bpf: Add stacktrace map lookup_and_delete_elem test case
  selftests/bpf: Refactor stacktrace_map case with skeleton
  bpf: Add lookup_and_delete_elem for BPF_MAP_STACK_TRACE
  selftests/bpf: Fix flaky bpf_cookie selftest
  selftests/bpf: Test changing packet data from global functions with a kfunc
  bpf: Emit struct bpf_xdp_sock type in vmlinux BTF
  selftests/bpf: Task_work selftest cleanup fixes
  MAINTAINERS: Delete inactive maintainers from AF_XDP
  bpf: Mark kfuncs as __noclone
  selftests/bpf: Add kprobe multi write ctx attach test
  selftests/bpf: Add kprobe write ctx attach test
  selftests/bpf: Add uprobe context ip register change test
  ...

bpf: Add lookup_and_delete_elem for BPF_MAP_STACK_TRACE

2025-09-25T23:12:14+00:00

The stacktrace map can be easily full, which will lead to failure in
obtaining the stack. In addition to increasing the size of the map,
another solution is to delete the stack_id after looking it up from
the user, so extend the existing bpf_map_lookup_and_delete_elem()
functionality to stacktrace map types.

Signed-off-by: Tao Chen 
Signed-off-by: Andrii Nakryiko 
Link: https://lore.kernel.org/bpf/20250925175030.1615837-1-chen.dylane@linux.dev