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| author | Sanghyun Park <sanghyun.park.cnu@gmail.com> | 2026-08-05 12:14:25 +0900 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2026-08-08 10:25:36 +0200 |
| commit | fa9dcacdcdf487f0ffef64bf67622f1caed509f1 (patch) | |
| tree | 32467a9da941995156a793f6df23dd03f206a30b /kernel/bpf/task_iter.c | |
| parent | 3f562c537e9ecf4bc5e206cfffc2cc047f1b7e94 (diff) | |
| download | linux-next-fa9dcacdcdf487f0ffef64bf67622f1caed509f1.tar.gz linux-next-fa9dcacdcdf487f0ffef64bf67622f1caed509f1.zip | |
bpf: Fix mmap_lock leak in irq_work path
stack_map_get_build_id_offset() introduced a per-CPU irq_work to defer
mmap_read_unlock() from NMI context, and bpf_find_vma() later reused the
same mmap_unlock_work. Both callers only check whether the work is busy
before taking mmap_lock, so a nested caller can reuse the slot before the
first caller queues it. Two read locks may then be acquired while only one
deferred unlock runs, leaking a read lock and blocking exit_mmap().
Reserve the per-CPU slot before mmap_read_trylock(). Use the same wrapper
in stackmap and bpf_find_vma() so both callers release the reservation on
trylock failure. Keep rejecting the slot while the irq_work remains busy.
Release it after the irq_work callback unlocks the mm.
Fixes: eac9153f2b58 ("bpf/stackmap: Fix deadlock with rq_lock in bpf_get_stack()")
Reported-by: syzbot+cdd6c0925e12b0af60cc@syzkaller.appspotmail.com
Reported-by: sashiko-bot@kernel.org
Signed-off-by: Sanghyun Park <sanghyun.park.cnu@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Closes: https://syzkaller.appspot.com/bug?extid=cdd6c0925e12b0af60cc
Closes: https://lore.kernel.org/r/20260630033745.B80201F000E9@smtp.kernel.org
Link: https://lore.kernel.org/bpf/20260805031425.2157475-2-sanghyun.park.cnu@gmail.com
Diffstat (limited to 'kernel/bpf/task_iter.c')
| -rw-r--r-- | kernel/bpf/task_iter.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index b256fb9c1214..13e1aabe6f88 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -753,9 +753,8 @@ static struct bpf_iter_reg task_vma_reg_info = { BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start, bpf_callback_t, callback_fn, void *, callback_ctx, u64, flags) { - struct mmap_unlock_irq_work *work = NULL; + struct mmap_unlock_irq_work *work; struct vm_area_struct *vma; - bool irq_work_busy = false; bool __maybe_unused mmput_needed = false; struct mm_struct *mm; int ret = -ENOENT; @@ -792,9 +791,14 @@ BPF_CALL_5(bpf_find_vma, struct task_struct *, task, u64, start, if (!mm) return -ENOENT; - irq_work_busy = bpf_mmap_unlock_get_irq_work(&work); + work = bpf_mmap_unlock_guard_get(); + if (IS_ERR(work)) { + ret = PTR_ERR(work); + goto out; + } - if (irq_work_busy || !mmap_read_trylock(mm)) { + if (!mmap_read_trylock(mm)) { + bpf_mmap_unlock_guard_put(work); ret = -EBUSY; goto out; } @@ -1191,6 +1195,8 @@ static void do_mmap_read_unlock(struct irq_work *entry) work = container_of(entry, struct mmap_unlock_irq_work, irq_work); mmap_read_unlock_non_owner(work->mm); + work->mm = NULL; + bpf_mmap_unlock_guard_put(work); } static int __init task_iter_init(void) |