audit: type=1800 audit(1546377351.826:30): pid=7559 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed(directio) comm="startpar" name="rmnologin" dev="sda1" ino=2423 res=0 ====================================================== WARNING: possible circular locking dependency detected 4.20.0+ #3 Not tainted ------------------------------------------------------ syz-executor242/7714 is trying to acquire lock: 00000000d375f441 (&pipe->mutex/1){+.+.}, at: __pipe_lock fs/pipe.c:83 [inline] 00000000d375f441 (&pipe->mutex/1){+.+.}, at: fifo_open+0x159/0xb00 fs/pipe.c:905 but task is already holding lock: 0000000087896e5c (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x55/0x120 fs/exec.c:1404 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&sig->cred_guard_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_interruptible_nested+0x16/0x20 kernel/locking/mutex.c:1109 proc_pid_attr_write+0x1fa/0x530 fs/proc/base.c:2565 __vfs_write+0x116/0xb40 fs/read_write.c:485 __kernel_write+0x110/0x3b0 fs/read_write.c:506 write_pipe_buf+0x180/0x240 fs/splice.c:797 splice_from_pipe_feed fs/splice.c:503 [inline] __splice_from_pipe+0x39a/0x7e0 fs/splice.c:627 splice_from_pipe+0x1ea/0x310 fs/splice.c:662 default_file_splice_write+0x3c/0x90 fs/splice.c:809 do_splice_from fs/splice.c:851 [inline] do_splice+0x64b/0x1410 fs/splice.c:1152 __do_sys_splice fs/splice.c:1419 [inline] __se_sys_splice fs/splice.c:1399 [inline] __ia32_sys_splice+0x2c4/0x330 fs/splice.c:1399 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x333/0xf98 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 -> #0 (&pipe->mutex/1){+.+.}: lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 __pipe_lock fs/pipe.c:83 [inline] fifo_open+0x159/0xb00 fs/pipe.c:905 do_dentry_open+0x48a/0x1210 fs/open.c:771 vfs_open+0xa0/0xd0 fs/open.c:880 do_last fs/namei.c:3418 [inline] path_openat+0x144f/0x5650 fs/namei.c:3534 do_filp_open+0x26f/0x370 fs/namei.c:3564 do_open_execat+0x20e/0x930 fs/exec.c:853 __do_execve_file.isra.0+0x181e/0x2510 fs/exec.c:1755 do_execveat_common fs/exec.c:1866 [inline] compat_do_execve fs/exec.c:1910 [inline] __do_compat_sys_execve fs/exec.c:1985 [inline] __se_compat_sys_execve fs/exec.c:1981 [inline] __ia32_compat_sys_execve+0x94/0xc0 fs/exec.c:1981 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x333/0xf98 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); *** DEADLOCK *** 1 lock held by syz-executor242/7714: #0: 0000000087896e5c (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds+0x55/0x120 fs/exec.c:1404 stack backtrace: CPU: 0 PID: 7714 Comm: syz-executor242 Not tainted 4.20.0+ #3 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1db/0x2d0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2350 [inline] __lock_acquire+0x3014/0x4a30 kernel/locking/lockdep.c:3338 lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 __pipe_lock fs/pipe.c:83 [inline] fifo_open+0x159/0xb00 fs/pipe.c:905 do_dentry_open+0x48a/0x1210 fs/open.c:771 vfs_open+0xa0/0xd0 fs/open.c:880 do_last fs/namei.c:3418 [inline] path_openat+0x144f/0x5650 fs/namei.c:3534 do_filp_open+0x26f/0x370 fs/namei.c:3564 do_open_execat+0x20e/0x930 fs/exec.c:853 __do_execve_file.isra.0+0x181e/0x2510 fs/exec.c:1755 do_execveat_common fs/exec.c:1866 [inline] compat_do_execve fs/exec.c:1910 [inline] __do_compat_sys_execve fs/exec.c:1985 [inline] __se_compat_sys_execve fs/exec.c:1981 [inline] __ia32_compat_sys_execve+0x94/0xc0 fs/exec.c:1981 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x333/0xf98 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 RIP: 0023:0xf7f7d869 Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 002b:00000000f7f581fc EFLAGS: 00000246 ORIG_RAX: 000000000000000b RAX: ffffffffffffffda RBX: 0000000020000340 RCX: 0000000000000000