====================================================== WARNING: possible circular locking dependency detected 4.19.0+ #74 Not tainted ------------------------------------------------------ syz-executor760/13861 is trying to acquire lock: 00000000abf54373 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_attr_write+0x28a/0x540 fs/proc/base.c:2565 but task is already holding lock: 00000000f76f21ed (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline] 00000000f76f21ed (&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+0x166/0x1700 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 __pipe_lock fs/pipe.c:83 [inline] fifo_open+0x15c/0xad0 fs/pipe.c:905 do_dentry_open+0x499/0x1250 fs/open.c:771 vfs_open+0xa0/0xd0 fs/open.c:880 do_last fs/namei.c:3418 [inline] path_openat+0x12bf/0x5160 fs/namei.c:3534 do_filp_open+0x255/0x380 fs/namei.c:3564 do_open_execat+0x221/0x8e0 fs/exec.c:853 __do_execve_file.isra.33+0x173f/0x2540 fs/exec.c:1755 do_execveat_common fs/exec.c:1866 [inline] do_execve fs/exec.c:1883 [inline] __do_sys_execve fs/exec.c:1964 [inline] __se_sys_execve fs/exec.c:1959 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 mutex_lock_interruptible_nested+0x16/0x20 kernel/locking/mutex.c:1109 proc_pid_attr_write+0x28a/0x540 fs/proc/base.c:2565 __vfs_write+0x119/0x9f0 fs/read_write.c:485 __kernel_write+0x10c/0x370 fs/read_write.c:506 write_pipe_buf+0x180/0x240 fs/splice.c:798 splice_from_pipe_feed fs/splice.c:503 [inline] __splice_from_pipe+0x38b/0x7c0 fs/splice.c:627 splice_from_pipe+0x1ec/0x340 fs/splice.c:662 default_file_splice_write+0x3c/0x90 fs/splice.c:810 do_splice_from fs/splice.c:852 [inline] do_splice+0x64a/0x1430 fs/splice.c:1148 __do_sys_splice fs/splice.c:1415 [inline] __se_sys_splice fs/splice.c:1395 [inline] __x64_sys_splice+0x2c1/0x330 fs/splice.c:1395 do_syscall_64+0x1b9/0x820 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-executor760/13861: #0: 00000000fde0fec6 (sb_writers#6){.+.+}, at: file_start_write include/linux/fs.h:2761 [inline] #0: 00000000fde0fec6 (sb_writers#6){.+.+}, at: do_splice+0xd2e/0x1430 fs/splice.c:1147 #1: 00000000f76f21ed (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline] #1: 00000000f76f21ed (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 fs/pipe.c:70 stack backtrace: CPU: 1 PID: 13861 Comm: syz-executor760 Not tainted 4.19.0+ #74 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+0x1c4/0x2b6 lib/dump_stack.c:113 print_circular_bug.isra.33.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1861 [inline] check_prevs_add kernel/locking/lockdep.c:1974 [inline] validate_chain kernel/locking/lockdep.c:2415 [inline] __lock_acquire+0x33e4/0x4ec0 kernel/locking/lockdep.c:3411 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072 mutex_lock_interruptible_nested+0x16/0x20 kernel/locking/mutex.c:1109 proc_pid_attr_write+0x28a/0x540 fs/proc/base.c:2565 __vfs_write+0x119/0x9f0 fs/read_write.c:485 __kernel_write+0x10c/0x370 fs/read_write.c:506 write_pipe_buf+0x180/0x240 fs/splice.c:798 splice_from_pipe_feed fs/splice.c:503 [inline] __splice_from_pipe+0x38b/0x7c0 fs/splice.c:627 splice_from_pipe+0x1ec/0x340 fs/splice.c:662 default_file_splice_write+0x3c/0x90 fs/splice.c:810 do_splice_from fs/splice.c:852 [inline] do_splice+0x64a/0x1430 fs/splice.c:1148 __do_sys_splice fs/splice.c:1415 [inline] __se_sys_splice fs/splice.c:1395 [inline] __x64_sys_splice+0x2c1/0x330 fs/splice.c:1395 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x448979 Code: e8 1c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 2b 01 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007feb031a5cd8 EFLAGS: 00000216 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 00000000006e49f8 RCX: 0000000000448979 RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00000000006e49f0 R08: 00003fffffffffff R09: 0000000000000000 R10: 00000000200002c0 R11: 0000000000000216 R12: 00000000006e49fc R13: 00007ffef8be85df R14: 00007feb031a69c0 R15: 0000000000000001