Warning: Permanently added '10.128.0.103' (ECDSA) to the list of known hosts. executing program [ 23.876270] [ 23.877970] ====================================================== [ 23.884264] [ INFO: possible circular locking dependency detected ] [ 23.890646] 4.4.174+ #4 Not tainted [ 23.894247] ------------------------------------------------------- [ 23.900776] syz-executor675/2067 is trying to acquire lock: [ 23.906485] (&pipe->mutex/1){+.+.+.}, at: [] fifo_open+0x15d/0xa00 [ 23.915073] [ 23.915073] but task is already holding lock: [ 23.921015] (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 23.930946] [ 23.930946] which lock already depends on the new lock. [ 23.930946] [ 23.939247] [ 23.939247] the existing dependency chain (in reverse order) is: [ 23.946840] -> #1 (&sig->cred_guard_mutex){+.+.+.}: [ 23.952503] [] lock_acquire+0x15e/0x450 [ 23.958798] [] mutex_lock_interruptible_nested+0xd2/0xce0 [ 23.966632] [] proc_pid_attr_write+0x1a8/0x2a0 [ 23.973495] [] __vfs_write+0x116/0x3d0 [ 23.979687] [] __kernel_write+0x112/0x370 [ 23.986115] [] write_pipe_buf+0x15d/0x1f0 [ 23.992545] [] __splice_from_pipe+0x37e/0x7a0 [ 23.999394] [] splice_from_pipe+0x108/0x170 [ 24.005996] [] default_file_splice_write+0x3c/0x80 [ 24.013238] [] SyS_splice+0xd71/0x13a0 [ 24.019412] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 24.026613] -> #0 (&pipe->mutex/1){+.+.+.}: [ 24.031705] [] __lock_acquire+0x37d6/0x4f50 [ 24.038296] [] lock_acquire+0x15e/0x450 [ 24.044553] [] mutex_lock_nested+0xc1/0xb80 [ 24.051164] [] fifo_open+0x15d/0xa00 [ 24.057145] [] do_dentry_open+0x38f/0xbd0 [ 24.063566] [] vfs_open+0x10b/0x210 [ 24.069480] [] path_openat+0x136f/0x4470 [ 24.075812] [] do_filp_open+0x1a1/0x270 [ 24.082586] [] do_open_execat+0x10c/0x6e0 [ 24.089006] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 24.096469] [] SyS_execve+0x42/0x50 [ 24.102380] [] return_from_execve+0x0/0x23 [ 24.108895] [ 24.108895] other info that might help us debug this: [ 24.108895] [ 24.117014] Possible unsafe locking scenario: [ 24.117014] [ 24.123054] CPU0 CPU1 [ 24.127705] ---- ---- [ 24.132345] lock(&sig->cred_guard_mutex); [ 24.136906] lock(&pipe->mutex/1); [ 24.143394] lock(&sig->cred_guard_mutex); [ 24.150474] lock(&pipe->mutex/1); [ 24.154465] [ 24.154465] *** DEADLOCK *** [ 24.154465] [ 24.160600] 1 lock held by syz-executor675/2067: [ 24.165338] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 24.175733] [ 24.175733] stack backtrace: [ 24.180207] CPU: 1 PID: 2067 Comm: syz-executor675 Not tainted 4.4.174+ #4 [ 24.187193] 0000000000000000 68d6868be16344dd ffff8801d4507530 ffffffff81aad1a1 [ 24.195193] ffffffff84057a80 ffff8800b7d40000 ffffffff83abd2b0 ffffffff83ab6860 [ 24.203193] ffffffff83abd2b0 ffff8801d4507580 ffffffff813abcda ffff8801d4507660 [ 24.211191] Call Trace: [ 24.213760] [] dump_stack+0xc1/0x120 [ 24.219166] [] print_circular_bug.cold+0x2f7/0x44e [ 24.225736] [] __lock_acquire+0x37d6/0x4f50 [ 24.231755] [] ? trace_hardirqs_on+0x10/0x10 [ 24.237792] [] ? do_filp_open+0x1a1/0x270 [ 24.243568] [] ? do_execveat_common.isra.0+0x6f6/0x1e90 [ 24.250559] [] ? SyS_execve+0x42/0x50 [ 24.255999] [] ? stub_execve+0x5/0x5 [ 24.261354] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 24.268093] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 24.274821] [] lock_acquire+0x15e/0x450 [ 24.280423] [] ? fifo_open+0x15d/0xa00 [ 24.285951] [] ? fifo_open+0x15d/0xa00 [ 24.291476] [] mutex_lock_nested+0xc1/0xb80 [ 24.297421] [] ? fifo_open+0x15d/0xa00 [ 24.302949] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 24.309676] [] ? mutex_trylock+0x500/0x500 [ 24.315536] [] ? fifo_open+0x24d/0xa00 [ 24.321063] [] ? fifo_open+0x28c/0xa00 [ 24.326587] [] fifo_open+0x15d/0xa00 [ 24.331928] [] do_dentry_open+0x38f/0xbd0 [ 24.337700] [] ? __inode_permission2+0x9e/0x250 [ 24.343992] [] ? pipe_release+0x250/0x250 [ 24.349778] [] vfs_open+0x10b/0x210 [ 24.355030] [] ? may_open.isra.0+0xe7/0x210 [ 24.360979] [] path_openat+0x136f/0x4470 [ 24.366664] [] ? depot_save_stack+0x1c3/0x5f0 [ 24.372797] [] ? may_open.isra.0+0x210/0x210 [ 24.378829] [] ? kmemdup+0x27/0x60 [ 24.384007] [] ? selinux_cred_prepare+0x43/0xa0 [ 24.390317] [] ? security_prepare_creds+0x83/0xc0 [ 24.396786] [] ? prepare_creds+0x228/0x2b0 [ 24.402645] [] ? prepare_exec_creds+0x12/0xf0 [ 24.408769] [] ? do_execveat_common.isra.0+0x2d6/0x1e90 [ 24.415764] [] ? stub_execve+0x5/0x5 [ 24.421117] [] ? kasan_kmalloc+0xb7/0xd0 [ 24.426805] [] ? kasan_slab_alloc+0xf/0x20 [ 24.432675] [] ? kmem_cache_alloc+0xdc/0x2c0 [ 24.438708] [] ? prepare_creds+0x28/0x2b0 [ 24.444481] [] ? prepare_exec_creds+0x12/0xf0 [ 24.450607] [] do_filp_open+0x1a1/0x270 [ 24.456207] [] ? save_stack_trace+0x26/0x50 [ 24.462154] [] ? user_path_mountpoint_at+0x50/0x50 [ 24.468718] [] ? SyS_execve+0x42/0x50 [ 24.474145] [] ? stub_execve+0x5/0x5 [ 24.479486] [] ? __lock_acquire+0xa4f/0x4f50 [ 24.485522] [] ? trace_hardirqs_on+0x10/0x10 [ 24.491556] [] ? rcu_read_lock_sched_held+0x10b/0x130 [ 24.498387] [] do_open_execat+0x10c/0x6e0 [ 24.504176] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 24.510915] [] ? setup_arg_pages+0x7b0/0x7b0 [ 24.516960] [] ? do_execveat_common.isra.0+0x6b8/0x1e90 [ 24.523996] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 24.530816] [] ? do_execveat_common.isra.0+0x422/0x1e90 [ 24.537806] [] ? __check_object_size+0x222/0x332 [ 24.544188] [] ? strncpy_from_user+0xd0/0x230 [ 24.550351] [] ? prepare_bprm_creds+0x120/0x120 [ 24.556662] [] ? getname_flags+0x232/0x550 [ 24.562650] [] SyS_execve+0x42/0x50 [ 24.567917] [] stub_execve+0x5/0x5 [ 24.573094] [] ? tracesys+0x88/0x8d