====================================================== WARNING: possible circular locking dependency detected 4.14.104+ #21 Not tainted ------------------------------------------------------ syz-executor.0/4859 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: -> #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.0/4859: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 stack backtrace: CPU: 1 PID: 4859 Comm: syz-executor.0 Not tainted 4.14.104+ #21 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 EXT4-fs (loop2): feature flags set on rev 0 fs, running e2fsck is recommended EXT4-fs (loop2): couldn't mount as ext2 due to feature incompatibilities F2FS-fs (loop4): Magic Mismatch, valid(0xf2f52010) - read(0x0) F2FS-fs (loop4): Can't find valid F2FS filesystem in 1th superblock F2FS-fs (loop4): Magic Mismatch, valid(0xf2f52010) - read(0x0) F2FS-fs (loop4): Can't find valid F2FS filesystem in 2th superblock F2FS-fs (loop4): Magic Mismatch, valid(0xf2f52010) - read(0x0) F2FS-fs (loop4): Can't find valid F2FS filesystem in 1th superblock F2FS-fs (loop4): Magic Mismatch, valid(0xf2f52010) - read(0x0) F2FS-fs (loop4): Can't find valid F2FS filesystem in 2th superblock ip6_tunnel: ip6tnl3 xmit: Local address not yet configured!