diff options
| author | Matt Fleming <matt@codeblueprint.co.uk> | 2020-04-07 10:54:13 +0100 |
|---|---|---|
| committer | Luis Claudio R. Goncalves <lgoncalv@redhat.com> | 2023-02-18 22:05:24 -0300 |
| commit | a3587b10c57f5c2670d30ea124e6fd5f2d8a0c4e (patch) | |
| tree | 954386db627ff89c3fe9a1cf550f244bd558fb81 /kernel | |
| parent | ffe9c3d5bf1d1148ddf50bbb5201f0333d35e063 (diff) | |
| download | linux-rt-a3587b10c57f5c2670d30ea124e6fd5f2d8a0c4e.tar.gz | |
signal: Prevent double-free of user struct
The way user struct reference counting works changed significantly with,
fda31c50292a ("signal: avoid double atomic counter increments for user accounting")
Now user structs are only freed once the last pending signal is
dequeued. Make sigqueue_free_current() follow this new convention to
avoid freeing the user struct multiple times and triggering this
warning:
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 6794 at lib/refcount.c:288 refcount_dec_not_one+0x45/0x50
Call Trace:
refcount_dec_and_lock_irqsave+0x16/0x60
free_uid+0x31/0xa0
__dequeue_signal+0x17c/0x190
dequeue_signal+0x5a/0x1b0
do_sigtimedwait+0x208/0x250
__x64_sys_rt_sigtimedwait+0x6f/0xd0
do_syscall_64+0x72/0x200
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Reported-by: Daniel Wagner <wagi@monom.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/signal.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/signal.c b/kernel/signal.c index e1f263cbcf09..a1eeecb4922d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -495,8 +495,8 @@ static void sigqueue_free_current(struct sigqueue *q) up = q->user; if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) { - atomic_dec(&up->sigpending); - free_uid(up); + if (atomic_dec_and_test(&up->sigpending)) + free_uid(up); } else __sigqueue_free(q); } |