====================================================== WARNING: possible circular locking dependency detected 5.0.0-rc6+ #68 Not tainted ------------------------------------------------------ syz-executor.2/3864 is trying to acquire lock: 00000000446830f1 (&sig->cred_guard_mutex){+.+.}, at: do_io_accounting+0x1f4/0x830 fs/proc/base.c:2711 ------------[ cut here ]------------ but task is already holding lock: downgrading a read lock WARNING: CPU: 0 PID: 3857 at kernel/locking/lockdep.c:3553 __lock_downgrade kernel/locking/lockdep.c:3553 [inline] WARNING: CPU: 0 PID: 3857 at kernel/locking/lockdep.c:3553 lock_downgrade+0x478/0x810 kernel/locking/lockdep.c:3816 000000003743ee55 (&p->lock){+.+.}, at: seq_read+0x71/0x1130 fs/seq_file.c:161 Kernel panic - not syncing: panic_on_warn set ... which lock already depends on the new lock. CPU: 0 PID: 3857 Comm: blkid Not tainted 5.0.0-rc6+ #68 the existing dependency chain (in reverse order) is: Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 -> #2 (&p->lock){+.+.}: Call Trace: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x71/0x1130 fs/seq_file.c:161 panic+0x2cb/0x65c kernel/panic.c:214 proc_reg_read+0x1fa/0x2c0 fs/proc/inode.c:229 do_loop_readv_writev fs/read_write.c:700 [inline] do_loop_readv_writev fs/read_write.c:687 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:921 vfs_readv+0xf0/0x160 fs/read_write.c:983 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x475/0x890 fs/splice.c:417 do_splice_to+0x12a/0x190 fs/splice.c:880 do_splice+0xf7c/0x1330 fs/splice.c:1178 __do_sys_splice fs/splice.c:1419 [inline] __se_sys_splice fs/splice.c:1399 [inline] __x64_sys_splice+0x2c6/0x330 fs/splice.c:1399 __warn.cold+0x20/0x45 kernel/panic.c:571 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe report_bug+0x263/0x2b0 lib/bug.c:186 -> #1 (&pipe->mutex/1){+.+.}: fixup_bug arch/x86/kernel/traps.c:178 [inline] fixup_bug arch/x86/kernel/traps.c:173 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290 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 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 do_dentry_open+0x47d/0x1130 fs/open.c:771 RIP: 0010:__lock_downgrade kernel/locking/lockdep.c:3553 [inline] RIP: 0010:lock_downgrade+0x478/0x810 kernel/locking/lockdep.c:3816 vfs_open+0xa0/0xd0 fs/open.c:880 Code: 4c 89 c6 4c 89 e7 e8 97 79 ff ff e9 32 ff ff ff 48 c7 c7 40 aa 6b 87 4c 89 8d 60 ff ff ff 48 89 85 68 ff ff ff e8 96 e5 eb ff <0f> 0b 8b 55 98 4c 8b 8d 60 ff ff ff 48 8b 85 68 ff ff ff e9 38 fe do_last fs/namei.c:3418 [inline] path_openat+0x10d7/0x4690 fs/namei.c:3534 RSP: 0018:ffff88804de77ce8 EFLAGS: 00010082 do_filp_open+0x1a1/0x280 fs/namei.c:3564 RAX: 0000000000000000 RBX: 1ffff11009bcefa2 RCX: 0000000000000000 do_open_execat+0x13b/0x6d0 fs/exec.c:856 RDX: 0000000000000000 RSI: ffffffff815a9266 RDI: ffffed1009bcef8f __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 RBP: ffff88804de77d98 R08: ffff8880a5ac8700 R09: fffffbfff1133341 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 R10: fffffbfff1133340 R11: ffffffff88999a03 R12: ffff8880a5ac8700 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 R13: ffffffff8a556aa0 R14: 0000000000000001 R15: ffff8880a5ac8f78 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_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2711 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2760 downgrade_write+0x19/0x160 kernel/locking/rwsem.c:147 proc_single_show+0xf6/0x180 fs/proc/base.c:739 __do_munmap+0xc5a/0xef0 mm/mmap.c:2823 seq_read+0x4db/0x1130 fs/seq_file.c:229 __vm_munmap+0xff/0x1a0 mm/mmap.c:2848 __vfs_read+0x116/0x8c0 fs/read_write.c:416 vfs_read+0x194/0x3e0 fs/read_write.c:452 ksys_pread64+0x183/0x1c0 fs/read_write.c:626 __do_sys_munmap mm/mmap.c:2873 [inline] __se_sys_munmap mm/mmap.c:2870 [inline] __x64_sys_munmap+0x67/0x80 mm/mmap.c:2870 __do_sys_pread64 fs/read_write.c:636 [inline] __se_sys_pread64 fs/read_write.c:633 [inline] __x64_sys_pread64+0x97/0xf0 fs/read_write.c:633 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fc98bce0417 other info that might help us debug this: Code: f0 ff ff 73 01 c3 48 8d 0d 8a ad 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 5d ad 20 00 31 d2 48 29 c2 89 Chain exists of: &sig->cred_guard_mutex --> &pipe->mutex/1 --> &p->lock RSP: 002b:00007fff645ba3e8 EFLAGS: 00000203 ORIG_RAX: 000000000000000b Possible unsafe locking scenario: RAX: ffffffffffffffda RBX: 00007fc98beeb1c8 RCX: 00007fc98bce0417 CPU0 CPU1 RDX: 00000000009dd700 RSI: 00000000000033ef RDI: 00007fc98bee3000 ---- ---- RBP: 00007fff645ba550 R08: 0000000000000001 R09: 0000000000000007 lock(&p->lock); R10: 00007fc98bcdaa0b R11: 0000000000000203 R12: 000000006df2186f lock(&pipe->mutex/1); R13: 000001f16df2186f R14: 000001f16d55bb3b R15: 00007fc98bee0740 lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor.2/3864: #0: 000000003743ee55 (&p->lock){+.+.}, at: seq_read+0x71/0x1130 fs/seq_file.c:161 stack backtrace: CPU: 1 PID: 3864 Comm: syz-executor.2 Not tainted 5.0.0-rc6+ #68 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_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2711 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2760 proc_single_show+0xf6/0x180 fs/proc/base.c:739 seq_read+0x4db/0x1130 fs/seq_file.c:229 __vfs_read+0x116/0x8c0 fs/read_write.c:416 vfs_read+0x194/0x3e0 fs/read_write.c:452 ksys_pread64+0x183/0x1c0 fs/read_write.c:626 __do_sys_pread64 fs/read_write.c:636 [inline] __se_sys_pread64 fs/read_write.c:633 [inline] __x64_sys_pread64+0x97/0xf0 fs/read_write.c:633 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457e39 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:00007feb0d10ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000011 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457e39 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007feb0d10f6d4 R13: 00000000004c4941 R14: 00000000004d8140 R15: 00000000ffffffff Kernel Offset: disabled Rebooting in 86400 seconds..