5.4.54-rt33-rc1 stable review patch. If anyone has any objections, please let me know.
------------------ From: Matt Fleming <[email protected]> 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 <[email protected]> Reported-by: Daniel Wagner <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- kernel/signal.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index def2e8e37f1f..aa924f0141cf 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -494,8 +494,8 @@ 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); } -- 2.28.0
