====================================================== WARNING: possible circular locking dependency detected 4.14.102+ #17 Not tainted ------------------------------------------------------ syz-executor.1/13150 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.1/13150: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 stack backtrace: CPU: 0 PID: 13150 Comm: syz-executor.1 Not tainted 4.14.102+ #17 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 netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'. netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'. FAT-fs (loop4): bogus number of reserved sectors FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): bogus number of reserved sectors FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): bogus number of reserved sectors FAT-fs (loop4): Can't find a valid FAT filesystem audit: type=1400 audit(1550734886.835:94): avc: denied { relabelto } for pid=13235 comm="syz-executor.1" name="UNIX" dev="sockfs" ino=34166 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:syslogd_var_lib_t:s0 tclass=unix_stream_socket permissive=1 FAT-fs (loop4): bogus number of reserved sectors FAT-fs (loop4): Can't find a valid FAT filesystem netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'. SELinux: unrecognized netlink message: protocol=6 nlmsg_type=0 sclass=netlink_xfrm_socket pig=13281 comm=syz-executor.5 FAT-fs (loop4): bogus number of reserved sectors netlink: 8 bytes leftover after parsing attributes in process `syz-executor.5'. FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem audit: type=1400 audit(1550734890.465:95): avc: denied { relabelto } for pid=13472 comm="syz-executor.5" name="UDPv6" dev="sockfs" ino=34497 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:logrotate_var_lib_t:s0 tclass=udp_socket permissive=1 FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=13522 comm=syz-executor.0 SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=13522 comm=syz-executor.0 FAT-fs (loop4): invalid media value (0x00) FAT-fs (loop4): Can't find a valid FAT filesystem FAT-fs (loop4): codepage cp437 not found FAT-fs (loop4): codepage cp437 not found FAT-fs (loop4): codepage cp437 not found FAT-fs (loop4): codepage cp437 not found FAT-fs (loop4): codepage cp437 not found FAT-fs (loop4): codepage cp437 not found SELinux: unrecognized netlink message: protocol=6 nlmsg_type=25959 sclass=netlink_xfrm_socket pig=13719 comm=syz-executor.5 SELinux: unrecognized netlink message: protocol=6 nlmsg_type=25959 sclass=netlink_xfrm_socket pig=13721 comm=syz-executor.5