======================================================
WARNING: possible circular locking dependency detected
4.14.105+ #28 Not tainted
------------------------------------------------------
syz-executor.3/5144 is trying to acquire lock:
(&sig->cred_guard_mutex){+.+.}, at: [<ffffffff8ba9ff72>] proc_pid_attr_write+0x152/0x280 fs/proc/base.c:2586
but task is already holding lock:
(&pipe->mutex/1){+.+.}, at: [<ffffffff8b970548>] pipe_lock_nested fs/pipe.c:67 [inline]
(&pipe->mutex/1){+.+.}, at: [<ffffffff8b970548>] pipe_lock+0x58/0x70 fs/pipe.c:75
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&pipe->mutex/1){+.+.}:
-> #0 (&sig->cred_guard_mutex){+.+.}:
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&pipe->mutex/1);
lock(&sig->cred_guard_mutex);
lock(&pipe->mutex/1);
lock(&sig->cred_guard_mutex);
*** DEADLOCK ***
2 locks held by syz-executor.3/5144:
#0: (sb_writers#7){.+.+}, at: [<ffffffff8b9fbb51>] file_start_write include/linux/fs.h:2726 [inline]
#0: (sb_writers#7){.+.+}, at: [<ffffffff8b9fbb51>] do_splice fs/splice.c:1146 [inline]
#0: (sb_writers#7){.+.+}, at: [<ffffffff8b9fbb51>] SYSC_splice fs/splice.c:1402 [inline]
#0: (sb_writers#7){.+.+}, at: [<ffffffff8b9fbb51>] SyS_splice+0xec1/0x12d0 fs/splice.c:1382
#1: (&pipe->mutex/1){+.+.}, at: [<ffffffff8b970548>] pipe_lock_nested fs/pipe.c:67 [inline]
#1: (&pipe->mutex/1){+.+.}, at: [<ffffffff8b970548>] pipe_lock+0x58/0x70 fs/pipe.c:75
stack backtrace:
CPU: 1 PID: 5144 Comm: syz-executor.3 Not tainted 4.14.105+ #28
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x10e lib/dump_stack.c:53
print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258