====================================================== WARNING: possible circular locking dependency detected 4.14.97+ #1 Not tainted ------------------------------------------------------ syz-executor5/16179 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-executor5/16179: #0: (&sig->cred_guard_mutex){+.+.}, at: [] prepare_bprm_creds+0x51/0x110 fs/exec.c:1389 stack backtrace: CPU: 0 PID: 16179 Comm: syz-executor5 Not tainted 4.14.97+ #1 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 input: syz1 as /devices/virtual/input/input50 input: syz1 as /devices/virtual/input/input51 SELinux: unrecognized netlink message: protocol=6 nlmsg_type=0 sclass=netlink_xfrm_socket pig=16249 comm=syz-executor3 SELinux: unrecognized netlink message: protocol=6 nlmsg_type=0 sclass=netlink_xfrm_socket pig=16262 comm=syz-executor3 binder: BINDER_SET_CONTEXT_MGR already set binder: 16278:16279 ioctl 40046207 0 returned -16 binder: BINDER_SET_CONTEXT_MGR already set binder: 16278:16279 ioctl 40046207 0 returned -16 audit: type=1400 audit(1549258866.321:110): avc: denied { setattr } for pid=16347 comm="syz-executor3" name="pagemap" dev="proc" ino=43814 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=file permissive=1 ip6_tunnel: ip6tnl1 xmit: Local address not yet configured! EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable ip6_tunnel: ip6tnl1 xmit: Local address not yet configured! EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable EXT4-fs (sda1): re-mounted. Opts: noquota,init_itable ip6_tunnel: ip6tnl2 xmit: Local address not yet configured!