====================================================== WARNING: possible circular locking dependency detected 4.14.109+ #46 Not tainted ------------------------------------------------------ syz-executor.4/1745 is trying to acquire lock: (&pipe->mutex/1){+.+.}, at: [<00000000c0613980>] __pipe_lock fs/pipe.c:88 [inline] (&pipe->mutex/1){+.+.}, at: [<00000000c0613980>] fifo_open+0x156/0x9b0 fs/pipe.c:935 but task is already holding lock: (&sig->cred_guard_mutex){+.+.}, at: [<00000000194204ed>] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&sig->cred_guard_mutex){+.+.}: -> #1 (&p->lock){+.+.}: -> #0 (&pipe->mutex/1){+.+.}: other info that might help us debug this: Chain exists of: &pipe->mutex/1 --> &p->lock --> &sig->cred_guard_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&p->lock); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); *** DEADLOCK *** 1 lock held by syz-executor.4/1745: #0: (&sig->cred_guard_mutex){+.+.}, at: [<00000000194204ed>] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 stack backtrace: CPU: 0 PID: 1745 Comm: syz-executor.4 Not tainted 4.14.109+ #46 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 audit: type=1400 audit(1554223451.103:73): avc: denied { map } for pid=1822 comm="syz-executor.0" path="socket:[101587]" dev="sockfs" ino=101587 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=key_socket permissive=1