====================================================== WARNING: possible circular locking dependency detected 5.0.0+ #6 Not tainted ------------------------------------------------------ syz-executor.1/27105 is trying to acquire lock: 00000000d106c65e (&sig->cred_guard_mutex){+.+.}, at: proc_pid_attr_write+0x1fa/0x530 fs/proc/base.c:2569 but task is already holding lock: 00000000a55d810a (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline] 00000000a55d810a (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 fs/pipe.c:70 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&pipe->mutex/1){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 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+0x47d/0x1130 fs/open.c:771 vfs_open+0xa0/0xd0 fs/open.c:880 do_last fs/namei.c:3418 [inline] path_openat+0x10d7/0x4690 fs/namei.c:3534 do_filp_open+0x1a1/0x280 fs/namei.c:3564 do_open_execat+0x13b/0x6d0 fs/exec.c:856 __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 do_execveat_common fs/exec.c:1865 [inline] do_execve fs/exec.c:1882 [inline] __do_sys_execve fs/exec.c:1963 [inline] __se_sys_execve fs/exec.c:1958 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1958 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 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:2569 __vfs_write+0x116/0x8e0 fs/read_write.c:485 __kernel_write+0x110/0x3b0 fs/read_write.c:506 write_pipe_buf+0x15d/0x1f0 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+0x108/0x170 fs/splice.c:662 default_file_splice_write+0x3c/0x90 fs/splice.c:809 do_splice_from fs/splice.c:851 [inline] do_splice+0x70a/0x1490 fs/splice.c:1158 __do_sys_splice fs/splice.c:1428 [inline] __se_sys_splice fs/splice.c:1408 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1408 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 2 locks held by syz-executor.1/27105: #0: 000000008b3adc10 (sb_writers#7){.+.+}, at: file_start_write include/linux/fs.h:2822 [inline] #0: 000000008b3adc10 (sb_writers#7){.+.+}, at: do_splice+0xdf9/0x1490 fs/splice.c:1157 #1: 00000000a55d810a (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline] #1: 00000000a55d810a (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 fs/pipe.c:70 stack backtrace: CPU: 1 PID: 27105 Comm: syz-executor.1 Not tainted 5.0.0+ #6 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+0x172/0x1f0 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+0x2f00/0x4700 kernel/locking/lockdep.c:3338 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 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:2569 __vfs_write+0x116/0x8e0 fs/read_write.c:485 __kernel_write+0x110/0x3b0 fs/read_write.c:506 write_pipe_buf+0x15d/0x1f0 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+0x108/0x170 fs/splice.c:662 default_file_splice_write+0x3c/0x90 fs/splice.c:809 do_splice_from fs/splice.c:851 [inline] do_splice+0x70a/0x1490 fs/splice.c:1158 __do_sys_splice fs/splice.c:1428 [inline] __se_sys_splice fs/splice.c:1408 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1408 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457e29 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fa2f6de7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000457e29 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 000000000073bf00 R08: 0000000008100000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa2f6de86d4 R13: 00000000004c6c75 R14: 00000000004db870 R15: 00000000ffffffff ------------[ cut here ]------------ downgrading a read lock WARNING: CPU: 1 PID: 27104 at kernel/locking/lockdep.c:3553 __lock_downgrade kernel/locking/lockdep.c:3553 [inline] WARNING: CPU: 1 PID: 27104 at kernel/locking/lockdep.c:3553 lock_downgrade+0x478/0x810 kernel/locking/lockdep.c:3816