Warning: Permanently added '10.128.0.53' (ECDSA) to the list of known hosts. executing program syzkaller login: [ 39.856208] [ 39.857990] ====================================================== [ 39.864388] [ INFO: possible circular locking dependency detected ] [ 39.871097] 4.4.174+ #17 Not tainted [ 39.874829] ------------------------------------------------------- [ 39.881359] syz-executor234/2099 is trying to acquire lock: [ 39.887045] (&pipe->mutex/1){+.+.+.}, at: [] fifo_open+0x15d/0xa00 [ 39.895720] [ 39.895720] but task is already holding lock: [ 39.901708] (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 39.911590] [ 39.911590] which lock already depends on the new lock. [ 39.911590] [ 39.919886] [ 39.919886] the existing dependency chain (in reverse order) is: [ 39.927620] -> #1 (&sig->cred_guard_mutex){+.+.+.}: [ 39.933485] [] lock_acquire+0x15e/0x450 [ 39.939741] [] mutex_lock_interruptible_nested+0xd2/0xce0 [ 39.947589] [] proc_pid_attr_write+0x1a8/0x2a0 [ 39.954463] [] __vfs_write+0x116/0x3d0 [ 39.960685] [] __kernel_write+0x112/0x370 [ 39.967536] [] write_pipe_buf+0x15d/0x1f0 [ 39.973965] [] __splice_from_pipe+0x37e/0x7a0 [ 39.980733] [] splice_from_pipe+0x108/0x170 [ 39.987377] [] default_file_splice_write+0x3c/0x80 [ 39.994589] [] SyS_splice+0xd71/0x13a0 [ 40.000755] [] do_fast_syscall_32+0x32d/0xa90 [ 40.007735] [] sysenter_flags_fixed+0xd/0x1a [ 40.014488] -> #0 (&pipe->mutex/1){+.+.+.}: [ 40.019584] [] __lock_acquire+0x37d6/0x4f50 [ 40.026290] [] lock_acquire+0x15e/0x450 [ 40.032543] [] mutex_lock_nested+0xc1/0xb80 [ 40.039237] [] fifo_open+0x15d/0xa00 [ 40.045228] [] do_dentry_open+0x38f/0xbd0 [ 40.051694] [] vfs_open+0x10b/0x210 [ 40.057596] [] path_openat+0x136f/0x4470 [ 40.064028] [] do_filp_open+0x1a1/0x270 [ 40.070374] [] do_open_execat+0x10c/0x6e0 [ 40.076793] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 40.084302] [] compat_SyS_execve+0x48/0x60 [ 40.090807] [] do_fast_syscall_32+0x32d/0xa90 [ 40.097625] [] sysenter_flags_fixed+0xd/0x1a [ 40.104496] [ 40.104496] other info that might help us debug this: [ 40.104496] [ 40.112619] Possible unsafe locking scenario: [ 40.112619] [ 40.118660] CPU0 CPU1 [ 40.123315] ---- ---- [ 40.128011] lock(&sig->cred_guard_mutex); [ 40.132554] lock(&pipe->mutex/1); [ 40.139071] lock(&sig->cred_guard_mutex); [ 40.146148] lock(&pipe->mutex/1); [ 40.150188] [ 40.150188] *** DEADLOCK *** [ 40.150188] [ 40.156228] 1 lock held by syz-executor234/2099: [ 40.161017] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [] prepare_bprm_creds+0x55/0x120 [ 40.171500] [ 40.171500] stack backtrace: [ 40.176119] CPU: 0 PID: 2099 Comm: syz-executor234 Not tainted 4.4.174+ #17 [ 40.183242] 0000000000000000 b43b05896539c922 ffff8800b1a474c0 ffffffff81aad1a1 [ 40.191315] ffffffff84057a80 ffff8801d56c97c0 ffffffff83abd2b0 ffffffff83ab66b0 [ 40.199368] ffffffff83abd2b0 ffff8800b1a47510 ffffffff813abcda ffff8800b1a475f0 [ 40.207534] Call Trace: [ 40.210102] [] dump_stack+0xc1/0x120 [ 40.215503] [] print_circular_bug.cold+0x2f7/0x44e [ 40.222300] [] __lock_acquire+0x37d6/0x4f50 [ 40.228257] [] ? trace_hardirqs_on+0x10/0x10 [ 40.234293] [] ? do_filp_open+0x1a1/0x270 [ 40.240072] [] ? do_execveat_common.isra.0+0x6f6/0x1e90 [ 40.247065] [] ? compat_SyS_execve+0x48/0x60 [ 40.253104] [] ? do_fast_syscall_32+0x32d/0xa90 [ 40.259398] [] ? sysenter_flags_fixed+0xd/0x1a [ 40.265800] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 40.272643] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 40.279399] [] lock_acquire+0x15e/0x450 [ 40.285039] [] ? fifo_open+0x15d/0xa00 [ 40.290568] [] ? fifo_open+0x15d/0xa00 [ 40.296122] [] mutex_lock_nested+0xc1/0xb80 [ 40.302086] [] ? fifo_open+0x15d/0xa00 [ 40.307605] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 40.314345] [] ? mutex_trylock+0x500/0x500 [ 40.320219] [] ? fifo_open+0x24d/0xa00 [ 40.325940] [] ? fifo_open+0x28c/0xa00 [ 40.331453] [] fifo_open+0x15d/0xa00 [ 40.336800] [] do_dentry_open+0x38f/0xbd0 [ 40.342575] [] ? __inode_permission2+0x9e/0x250 [ 40.348868] [] ? pipe_release+0x250/0x250 [ 40.354645] [] vfs_open+0x10b/0x210 [ 40.359899] [] ? may_open.isra.0+0xe7/0x210 [ 40.365851] [] path_openat+0x136f/0x4470 [ 40.371539] [] ? depot_save_stack+0x1c3/0x5f0 [ 40.377705] [] ? may_open.isra.0+0x210/0x210 [ 40.383813] [] ? kmemdup+0x27/0x60 [ 40.388985] [] ? selinux_cred_prepare+0x43/0xa0 [ 40.395286] [] ? security_prepare_creds+0x83/0xc0 [ 40.401763] [] ? prepare_creds+0x228/0x2b0 [ 40.407708] [] ? prepare_exec_creds+0x12/0xf0 [ 40.413876] [] ? do_execveat_common.isra.0+0x2d6/0x1e90 [ 40.420877] [] ? do_fast_syscall_32+0x32d/0xa90 [ 40.427285] [] ? kasan_kmalloc+0xb7/0xd0 [ 40.432978] [] ? kasan_slab_alloc+0xf/0x20 [ 40.438844] [] ? kmem_cache_alloc+0xdc/0x2c0 [ 40.444886] [] ? prepare_creds+0x28/0x2b0 [ 40.450832] [] ? prepare_exec_creds+0x12/0xf0 [ 40.457027] [] do_filp_open+0x1a1/0x270 [ 40.462697] [] ? save_stack_trace+0x26/0x50 [ 40.468650] [] ? user_path_mountpoint_at+0x50/0x50 [ 40.475219] [] ? compat_SyS_execve+0x48/0x60 [ 40.481261] [] ? do_fast_syscall_32+0x32d/0xa90 [ 40.487564] [] ? sysenter_flags_fixed+0xd/0x1a [ 40.493792] [] ? __lock_acquire+0xa4f/0x4f50 [ 40.499834] [] ? trace_hardirqs_on+0x10/0x10 [ 40.505878] [] ? rcu_read_lock_sched_held+0x10b/0x130 [ 40.512701] [] do_open_execat+0x10c/0x6e0 [ 40.518587] [] ? debug_lockdep_rcu_enabled+0x71/0xa0 [ 40.525419] [] ? setup_arg_pages+0x7b0/0x7b0 [ 40.531462] [] ? do_execveat_common.isra.0+0x6b8/0x1e90 [ 40.538460] [] do_execveat_common.isra.0+0x6f6/0x1e90 [ 40.545329] [] ? do_execveat_common.isra.0+0x422/0x1e90 [ 40.552333] [] ? __check_object_size+0x222/0x332 [ 40.558717] [] ? strncpy_from_user+0xd1/0x230 [ 40.564835] [] ? prepare_bprm_creds+0x120/0x120 [ 40.571135] [] ? getname_flags+0x232/0x550 [ 40.577003] [] compat_SyS_execve+0x48/0x60 [ 40.582867] [] ? SyS_execveat+0x70/0x70 [ 40.588470] [] do_fast_syscall_32+0x32d/0xa90 [ 40.594790] [] sysenter_flags_fixed+0xd/0x1a