====================================================== WARNING: possible circular locking dependency detected 4.14.107+ #32 Not tainted ------------------------------------------------------ syz-executor.2/19856 is trying to acquire lock: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] (&pipe->mutex/1){+.+.}, at: [] fifo_open+0x156/0x9b0 fs/pipe.c:921 but task is already holding lock: (&sig->cred_guard_mutex){+.+.}, at: [] 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: -> #1 (&sig->cred_guard_mutex){+.+.}: -> #0 (&pipe->mutex/1){+.+.}: other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); *** DEADLOCK *** 1 lock held by syz-executor.2/19856: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 stack backtrace: CPU: 0 PID: 19856 Comm: syz-executor.2 Not tainted 4.14.107+ #32 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=1326 audit(1553044273.163:106): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=19854 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044273.523:107): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=19912 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044274.343:108): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=19975 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044275.163:109): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=20030 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044275.983:110): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=20086 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044276.793:111): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=20149 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044277.623:112): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=20218 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0xffff0000 audit: type=1326 audit(1553044282.043:113): auid=4294967295 uid=0 gid=0 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 pid=20630 comm="syz-executor.0" exe="/root/syz-executor.0" sig=31 arch=c000003e syscall=228 compat=0 ip=0x45aeda code=0x0