Warning: Permanently added '10.128.0.189' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 42.115564] [ 42.117235] ====================================================== [ 42.123526] [ INFO: possible circular locking dependency detected ] [ 42.129908] 4.4.167+ #4 Not tainted [ 42.133505] ------------------------------------------------------- [ 42.139883] syz-executor136/2083 is trying to acquire lock: [ 42.145567] (&pipe->mutex/1){+.+.+.}, at: [] fifo_open+0x15c/0x9e0 [ 42.154120] [ 42.154120] but task is already holding lock: [ 42.160171] (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x53/0x110 [ 42.169989] [ 42.169989] which lock already depends on the new lock. [ 42.169989] [ 42.178280] [ 42.178280] the existing dependency chain (in reverse order) is: [ 42.185879] -> #1 (&sig->cred_guard_mutex){+.+.+.}: [ 42.191512] [] lock_acquire+0x15e/0x450 [ 42.197749] [] mutex_lock_interruptible_nested+0xd2/0xcc0 [ 42.205553] [] proc_pid_attr_write+0x19e/0x290 [ 42.212397] [] __vfs_write+0x11c/0x3e0 [ 42.218553] [] __kernel_write+0x10a/0x350 [ 42.224964] [] write_pipe_buf+0x15d/0x1f0 [ 42.231373] [] __splice_from_pipe+0x364/0x790 [ 42.238132] [] splice_from_pipe+0xf9/0x170 [ 42.244634] [] default_file_splice_write+0x3c/0x80 [ 42.251830] [] SyS_splice+0xde1/0x1430 [ 42.257981] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 42.265196] -> #0 (&pipe->mutex/1){+.+.+.}: [ 42.270296] [] __lock_acquire+0x3cd4/0x5530 [ 42.276878] [] lock_acquire+0x15e/0x450 [ 42.283117] [] mutex_lock_nested+0xc2/0xb60 [ 42.289701] [] fifo_open+0x15c/0x9e0 [ 42.295679] [] do_dentry_open+0x38d/0xbd0 [ 42.302094] [] vfs_open+0x12a/0x210 [ 42.307980] [] path_openat+0xc10/0x3f10 [ 42.314217] [] do_filp_open+0x197/0x270 [ 42.320456] [] do_open_execat+0x10f/0x6f0 [ 42.326865] [] do_execveat_common.isra.14+0x6a1/0x1f00 [ 42.334404] [] SyS_execve+0x42/0x50 [ 42.340290] [] return_from_execve+0x0/0x23 [ 42.346789] [ 42.346789] other info that might help us debug this: [ 42.346789] [ 42.354903] Possible unsafe locking scenario: [ 42.354903] [ 42.360932] CPU0 CPU1 [ 42.365574] ---- ---- [ 42.370216] lock(&sig->cred_guard_mutex); [ 42.374826] lock(&pipe->mutex/1); [ 42.381305] lock(&sig->cred_guard_mutex); [ 42.388353] lock(&pipe->mutex/1); [ 42.392304] [ 42.392304] *** DEADLOCK *** [ 42.392304] [ 42.398341] 1 lock held by syz-executor136/2083: [ 42.403069] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x53/0x110 [ 42.413626] [ 42.413626] stack backtrace: [ 42.418098] CPU: 0 PID: 2083 Comm: syz-executor136 Not tainted 4.4.167+ #4 [ 42.425079] 0000000000000000 0a204da37d3c02f4 ffff8801d39af4d0 ffffffff81aa62cd [ 42.433056] ffffffff83ab7610 ffffffff83ab7610 ffff8801d40117c0 ffffffff83ab0860 [ 42.441036] ffff8801d40120a8 ffff8801d39af520 ffffffff813a9559 ffff8801d40117c0 [ 42.449023] Call Trace: [ 42.451592] [] dump_stack+0xc1/0x124 [ 42.457056] [] print_circular_bug.cold.31+0x2f6/0x435 [ 42.463873] [] __lock_acquire+0x3cd4/0x5530 [ 42.469819] [] ? trace_hardirqs_on+0x10/0x10 [ 42.475853] [] ? path_openat+0xc10/0x3f10 [ 42.481631] [] ? do_open_execat+0x10f/0x6f0 [ 42.487590] [] ? do_execveat_common.isra.14+0x6a1/0x1f00 [ 42.494673] [] lock_acquire+0x15e/0x450 [ 42.500434] [] ? fifo_open+0x15c/0x9e0 [ 42.505946] [] mutex_lock_nested+0xc2/0xb60 [ 42.511931] [] ? fifo_open+0x15c/0x9e0 [ 42.517631] [] ? check_preemption_disabled+0x3b/0x200 [ 42.524506] [] ? lockdep_init_map+0x110/0x1630 [ 42.530726] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 42.537454] [] ? mutex_trylock+0x4f0/0x4f0 [ 42.543310] [] ? fifo_open+0x24e/0x9e0 [ 42.548881] [] ? fifo_open+0x28d/0x9e0 [ 42.554508] [] fifo_open+0x15c/0x9e0 [ 42.559852] [] do_dentry_open+0x38d/0xbd0 [ 42.565621] [] ? __inode_permission2+0x9b/0x240 [ 42.571912] [] ? pipe_release+0x250/0x250 [ 42.577688] [] vfs_open+0x12a/0x210 [ 42.582937] [] ? may_open.isra.19+0x156/0x240 [ 42.589053] [] path_openat+0xc10/0x3f10 [ 42.594656] [] ? dump_trace+0x184/0x360 [ 42.600309] [] ? may_open.isra.19+0x240/0x240 [ 42.606438] [] ? kasan_kmalloc.part.1+0xc9/0xf0 [ 42.612738] [] ? save_stack_trace+0x26/0x50 [ 42.618688] [] ? kasan_kmalloc.part.1+0x62/0xf0 [ 42.624978] [] ? kasan_kmalloc+0xaf/0xc0 [ 42.630668] [] ? __kmalloc_track_caller+0xf1/0x2e0 [ 42.637219] [] ? kmemdup+0x24/0x50 [ 42.642385] [] ? selinux_cred_prepare+0x43/0xa0 [ 42.648700] [] ? security_prepare_creds+0x83/0xc0 [ 42.655171] [] ? prepare_creds+0x222/0x2a0 [ 42.661028] [] ? prepare_exec_creds+0x11/0xf0 [ 42.667149] [] ? prepare_bprm_creds+0x67/0x110 [ 42.673356] [] ? SyS_execve+0x42/0x50 [ 42.678779] [] ? stub_execve+0x5/0x5 [ 42.684118] [] ? save_stack_trace+0x26/0x50 [ 42.690060] [] ? kasan_kmalloc+0xaf/0xc0 [ 42.695751] [] ? kasan_slab_alloc+0x12/0x20 [ 42.701699] [] ? kmem_cache_alloc+0xdc/0x2c0 [ 42.707730] [] ? prepare_creds+0x28/0x2a0 [ 42.713612] [] ? prepare_exec_creds+0x11/0xf0 [ 42.719750] [] ? prepare_bprm_creds+0x67/0x110 [ 42.725963] [] ? do_execveat_common.isra.14+0x2d8/0x1f00 [ 42.733038] [] ? save_stack_trace+0x26/0x50 [ 42.738985] [] do_filp_open+0x197/0x270 [ 42.744587] [] ? user_path_mountpoint_at+0x70/0x70 [ 42.751204] [] ? trace_hardirqs_on+0x10/0x10 [ 42.757242] [] ? rcu_read_lock_sched_held+0x103/0x120 [ 42.764057] [] do_open_execat+0x10f/0x6f0 [ 42.769828] [] ? debug_lockdep_rcu_enabled+0x77/0x90 [ 42.776553] [] ? setup_arg_pages+0x7a0/0x7a0 [ 42.782583] [] do_execveat_common.isra.14+0x6a1/0x1f00 [ 42.789485] [] ? do_execveat_common.isra.14+0x3db/0x1f00 [ 42.796558] [] ? prepare_bprm_creds+0x110/0x110 [ 42.802851] [] ? getname_flags+0x229/0x550 [ 42.808793] [] ? retint_user+0x18/0x3c [ 42.814311] [] SyS_execve+0x42/0x50 [ 42.819561] [] stub_execve+0x5/0x5 [ 42.824759] [] ? tracesys+0x88/0x8d