====================================================== WARNING: possible circular locking dependency detected 4.14.98+ #7 Not tainted ------------------------------------------------------ syz-executor.0/21919 is trying to acquire lock: (&p->lock){+.+.}, at: [] seq_read+0xcd/0x1180 fs/seq_file.c:165 but task is already holding lock: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] (&pipe->mutex/1){+.+.}, at: [] pipe_lock+0x58/0x70 fs/pipe.c:75 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&pipe->mutex/1){+.+.}: -> #1 (&sig->cred_guard_mutex){+.+.}: -> #0 (&p->lock){+.+.}: other info that might help us debug this: Chain exists of: &p->lock --> &sig->cred_guard_mutex --> &pipe->mutex/1 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor.0/21919: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock+0x58/0x70 fs/pipe.c:75 stack backtrace: CPU: 1 PID: 21919 Comm: syz-executor.0 Not tainted 4.14.98+ #7 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