====================================================== WARNING: possible circular locking dependency detected 4.14.106+ #30 Not tainted ------------------------------------------------------ syz-executor.1/11514 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] do_io_accounting+0x1da/0x790 fs/proc/base.c:2727 FAT-fs (loop2): bogus number of reserved sectors but task is already holding lock: FAT-fs (loop2): Can't find a valid FAT filesystem (&p->lock){+.+.}, at: [] seq_read+0xcd/0x1180 fs/seq_file.c:165 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&p->lock){+.+.}: -> #1 (&pipe->mutex/1){+.+.}: -> #0 (&sig->cred_guard_mutex){+.+.}: other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> &pipe->mutex/1 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(&pipe->mutex/1); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor.1/11514: #0: (&p->lock){+.+.}, at: [] seq_read+0xcd/0x1180 fs/seq_file.c:165 stack backtrace: CPU: 1 PID: 11514 Comm: syz-executor.1 Not tainted 4.14.106+ #30 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 FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem FAT-fs (loop2): bogus number of reserved sectors FAT-fs (loop2): Can't find a valid FAT filesystem