Warning: Permanently added '10.128.0.89' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 38.409306] [ 38.411005] ====================================================== [ 38.417344] [ INFO: possible circular locking dependency detected ] [ 38.423784] 4.4.174+ #4 Not tainted [ 38.427391] ------------------------------------------------------- [ 38.433774] syz-executor366/2077 is trying to acquire lock: [ 38.439458] (&pipe->mutex/1){+.+.+.}, at: [] fifo_open+0x15d/0xa00 [ 38.448018] [ 38.448018] but task is already holding lock: [ 38.454091] (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 38.463969] [ 38.463969] which lock already depends on the new lock. [ 38.463969] [ 38.472264] [ 38.472264] the existing dependency chain (in reverse order) is: [ 38.479979] -> #1 (&sig->cred_guard_mutex){+.+.+.}: [ 38.485694] [] lock_acquire+0x15e/0x450 [ 38.491940] [] mutex_lock_interruptible_nested+0xd2/0xce0 [ 38.499762] [] proc_pid_attr_write+0x1a8/0x2a0 [ 38.506627] [] __vfs_write+0x116/0x3d0 [ 38.512797] [] __kernel_write+0x112/0x370 [ 38.519308] [] write_pipe_buf+0x15d/0x1f0 [ 38.525817] [] __splice_from_pipe+0x37e/0x7a0 [ 38.532624] [] splice_from_pipe+0x108/0x170 [ 38.539265] [] default_file_splice_write+0x3c/0x80 [ 38.546489] [] SyS_splice+0xd71/0x13a0 [ 38.552655] [] entry_SYSCALL_64_fastpath+0x1e/0x9a [ 38.559862] -> #0 (&pipe->mutex/1){+.+.+.}: [ 38.565037] [] __lock_acquire+0x37d6/0x4f50 [ 38.571645] [] lock_acquire+0x15e/0x450 [ 38.577902] [] mutex_lock_nested+0xc1/0xb80 [ 38.584498] [] fifo_open+0x15d/0xa00 [ 38.590543] [] do_dentry_open+0x38f/0xbd0 [ 38.596973] [] vfs_open+0x10b/0x210 [ 38.602877] [] path_openat+0x136f/0x4470 [ 38.609282] [] do_filp_open+0x1a1/0x270 [ 38.615542] [] do_open_execat+0x10c/0x6e0 [ 38.621969] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 38.629515] [] SyS_execve+0x42/0x50 [ 38.635497] [] return_from_execve+0x0/0x23 [ 38.642016] [ 38.642016] other info that might help us debug this: [ 38.642016] [ 38.650173] Possible unsafe locking scenario: [ 38.650173] [ 38.656216] CPU0 CPU1 [ 38.660864] ---- ---- [ 38.665508] lock(&sig->cred_guard_mutex); [ 38.670041] lock(&pipe->mutex/1); [ 38.676531] lock(&sig->cred_guard_mutex); [ 38.683579] lock(&pipe->mutex/1); [ 38.687539] [ 38.687539] *** DEADLOCK *** [ 38.687539] [ 38.693649] 1 lock held by syz-executor366/2077: [ 38.698522] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 38.708926] [ 38.708926] stack backtrace: [ 38.713401] CPU: 0 PID: 2077 Comm: syz-executor366 Not tainted 4.4.174+ #4 [ 38.720438] 0000000000000000 8cdf25ee026bbb30 ffff8800b6fff530 ffffffff81aad1a1 [ 38.728462] ffffffff84057a80 ffff8801d5d8af80 ffffffff83abd100 ffffffff83ab6500 [ 38.736455] ffffffff83abd100 ffff8800b6fff580 ffffffff813abcda ffff8800b6fff660 [ 38.744454] Call Trace: [ 38.747024] [] dump_stack+0xc1/0x120 [ 38.752375] [] print_circular_bug.cold+0x2f7/0x44e [ 38.758938] [] __lock_acquire+0x37d6/0x4f50 [ 38.764944] [] ? trace_hardirqs_on+0x10/0x10 [ 38.771128] [] ? do_filp_open+0x1a1/0x270 [ 38.776918] [] ? do_execveat_common.isra.0+0x6f6/0x1e90 [ 38.783924] [] ? SyS_execve+0x42/0x50 [ 38.789354] [] ? stub_execve+0x5/0x5 [ 38.794818] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 38.801571] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 38.808317] [] lock_acquire+0x15e/0x450 [ 38.813923] [] ? fifo_open+0x15d/0xa00 [ 38.819448] [] ? fifo_open+0x15d/0xa00 [ 38.824982] [] mutex_lock_nested+0xc1/0xb80 [ 38.830960] [] ? fifo_open+0x15d/0xa00 [ 38.836485] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 38.843262] [] ? mutex_trylock+0x500/0x500 [ 38.849177] [] ? fifo_open+0x24d/0xa00 [ 38.854723] [] ? fifo_open+0x28c/0xa00 [ 38.860251] [] fifo_open+0x15d/0xa00 [ 38.865595] [] do_dentry_open+0x38f/0xbd0 [ 38.871373] [] ? __inode_permission2+0x9e/0x250 [ 38.877699] [] ? pipe_release+0x250/0x250 [ 38.883494] [] vfs_open+0x10b/0x210 [ 38.888755] [] ? may_open.isra.0+0xe7/0x210 [ 38.894754] [] path_openat+0x136f/0x4470 [ 38.900457] [] ? depot_save_stack+0x1c3/0x5f0 [ 38.906607] [] ? may_open.isra.0+0x210/0x210 [ 38.912656] [] ? kmemdup+0x27/0x60 [ 38.917907] [] ? selinux_cred_prepare+0x43/0xa0 [ 38.924234] [] ? security_prepare_creds+0x83/0xc0 [ 38.930724] [] ? prepare_creds+0x228/0x2b0 [ 38.936648] [] ? prepare_exec_creds+0x12/0xf0 [ 38.942792] [] ? do_execveat_common.isra.0+0x2d6/0x1e90 [ 38.949790] [] ? stub_execve+0x5/0x5 [ 38.955148] [] ? kasan_kmalloc+0xb7/0xd0 [ 38.960857] [] ? kasan_slab_alloc+0xf/0x20 [ 38.966743] [] ? kmem_cache_alloc+0xdc/0x2c0 [ 38.972799] [] ? prepare_creds+0x28/0x2b0 [ 38.978597] [] ? prepare_exec_creds+0x12/0xf0 [ 38.984737] [] do_filp_open+0x1a1/0x270 [ 38.990348] [] ? save_stack_trace+0x26/0x50 [ 38.996304] [] ? user_path_mountpoint_at+0x50/0x50 [ 39.002876] [] ? SyS_execve+0x42/0x50 [ 39.008315] [] ? stub_execve+0x5/0x5 [ 39.013672] [] ? __lock_acquire+0xa4f/0x4f50 [ 39.019727] [] ? trace_hardirqs_on+0x10/0x10 [ 39.025766] [] ? rcu_read_lock_sched_held+0x10b/0x130 [ 39.032596] [] do_open_execat+0x10c/0x6e0 [ 39.038380] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 39.045172] [] ? setup_arg_pages+0x7b0/0x7b0 [ 39.051219] [] ? do_execveat_common.isra.0+0x6b8/0x1e90 [ 39.058219] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 39.065086] [] ? do_execveat_common.isra.0+0x422/0x1e90 [ 39.072095] [] ? __check_object_size+0x222/0x332 [ 39.078529] [] ? strncpy_from_user+0xd0/0x230 [ 39.084666] [] ? prepare_bprm_creds+0x120/0x120 [ 39.090980] [] ? getname_flags+0x232/0x550 [ 39.096857] [] SyS_execve+0x42/0x50 [ 39.102119] [] stub_execve+0x5/0x5 [ 39.107288] [] ? tracesys+0x88/0x8d