possible deadlock in pipe

possible deadlock in pipe_lock (2)
Status: auto-closed as invalid on 2019/10/18 15:02
Reported-by: syzbot+31d8b84465a7cbfd8515@syzkaller.appspotmail.com
First crash: 307d, last: 235d

duplicates (1):
Title	Repro	Bisected	Count	Last	Reported	Patched	Status
possible deadlock in ovl_write_iter	C		222	218d	441d	0/16	closed as dup on 2019/02/12 15:47

similar bugs (4):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
upstream	possible deadlock in pipe_lock			50806	724d	772d	0/16	closed as invalid on 2018/02/14 14:20
android-49	possible deadlock in pipe_lock			5	49d	242d	0/3	public: reported on 2019/04/14 09:30
linux-4.19	possible deadlock in pipe_lock	C	fix	2	228d	231d	1/1	fixed on 2019/11/29 10:34
android-44	possible deadlock in pipe_lock	C		82	9d09h	242d	0/2	public: reported C repro on 2019/04/14 08:51

Sample crash report:

======================================================
WARNING: possible circular locking dependency detected
5.1.0-rc5+ #78 Not tainted
------------------------------------------------------
syz-executor.0/6771 is trying to acquire lock:
00000000b1c51315 (&pipe->mutex/1){+.+.}, at: pipe_lock_nested fs/pipe.c:62 [inline]
00000000b1c51315 (&pipe->mutex/1){+.+.}, at: pipe_lock+0x6e/0x80 fs/pipe.c:70

but task is already holding lock:
0000000041406b3c (sb_writers#5){.+.+}, at: file_start_write include/linux/fs.h:2825 [inline]
0000000041406b3c (sb_writers#5){.+.+}, at: do_splice+0xe23/0x1420 fs/splice.c:1153

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (sb_writers#5){.+.+}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
       percpu_down_read include/linux/percpu-rwsem.h:36 [inline]
       __sb_start_write+0x20b/0x360 fs/super.c:1613
       sb_start_write include/linux/fs.h:1621 [inline]
       mnt_want_write+0x3f/0xc0 fs/namespace.c:358
       ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24
       ovl_create_object+0xb3/0x2c0 fs/overlayfs/dir.c:599
       ovl_create+0x28/0x30 fs/overlayfs/dir.c:630
       lookup_open+0x12e0/0x1b10 fs/namei.c:3232
       do_last fs/namei.c:3322 [inline]
       path_openat+0x14ac/0x46e0 fs/namei.c:3533
       do_filp_open+0x1a1/0x280 fs/namei.c:3563
       do_sys_open+0x3fe/0x5d0 fs/open.c:1069
       ksys_open include/linux/syscalls.h:1373 [inline]
       __do_sys_creat fs/open.c:1127 [inline]
       __se_sys_creat fs/open.c:1125 [inline]
       __x64_sys_creat+0x61/0x80 fs/open.c:1125
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #3 (&ovl_i_mutex_dir_key[depth]){++++}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
       down_read+0x3b/0x90 kernel/locking/rwsem.c:24
       inode_lock_shared include/linux/fs.h:782 [inline]
       do_last fs/namei.c:3321 [inline]
       path_openat+0x1e98/0x46e0 fs/namei.c:3533
       do_filp_open+0x1a1/0x280 fs/namei.c:3563
       do_open_execat+0x137/0x690 fs/exec.c:856
       __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758
       do_execveat_common fs/exec.c:1865 [inline]
       do_execveat fs/exec.c:1893 [inline]
       __do_sys_execveat fs/exec.c:1969 [inline]
       __se_sys_execveat fs/exec.c:1961 [inline]
       __x64_sys_execveat+0xed/0x130 fs/exec.c:1961
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (&sig->cred_guard_mutex){+.+.}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
       __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
       lock_trace+0x4a/0xe0 fs/proc/base.c:388
       proc_pid_syscall+0x8a/0x220 fs/proc/base.c:623
       proc_single_show+0xf6/0x170 fs/proc/base.c:744
       seq_read+0x4db/0x1130 fs/seq_file.c:229
       do_loop_readv_writev fs/read_write.c:701 [inline]
       do_loop_readv_writev fs/read_write.c:688 [inline]
       do_iter_read+0x4a9/0x660 fs/read_write.c:922
       vfs_readv+0xf0/0x160 fs/read_write.c:984
       kernel_readv fs/splice.c:358 [inline]
       default_file_splice_read+0x475/0x890 fs/splice.c:413
       do_splice_to+0x12a/0x190 fs/splice.c:876
       splice_direct_to_actor+0x2d2/0x970 fs/splice.c:953
       do_splice_direct+0x1da/0x2a0 fs/splice.c:1062
       do_sendfile+0x597/0xd00 fs/read_write.c:1443
       __do_sys_sendfile64 fs/read_write.c:1504 [inline]
       __se_sys_sendfile64 fs/read_write.c:1490 [inline]
       __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1490
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&p->lock){+.+.}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
       __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
       seq_read+0x71/0x1130 fs/seq_file.c:161
       proc_reg_read+0x1fe/0x2c0 fs/proc/inode.c:227
       do_loop_readv_writev fs/read_write.c:701 [inline]
       do_loop_readv_writev fs/read_write.c:688 [inline]
       do_iter_read+0x4a9/0x660 fs/read_write.c:922
       vfs_readv+0xf0/0x160 fs/read_write.c:984
       kernel_readv fs/splice.c:358 [inline]
       default_file_splice_read+0x475/0x890 fs/splice.c:413
       do_splice_to+0x12a/0x190 fs/splice.c:876
       do_splice+0x110b/0x1420 fs/splice.c:1183
       __do_sys_splice fs/splice.c:1424 [inline]
       __se_sys_splice fs/splice.c:1404 [inline]
       __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404
       do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&pipe->mutex/1){+.+.}:
       check_prevs_add kernel/locking/lockdep.c:2333 [inline]
       validate_chain kernel/locking/lockdep.c:2714 [inline]
       __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3701
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
       __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_nested fs/pipe.c:62 [inline]
       pipe_lock+0x6e/0x80 fs/pipe.c:70
       iter_file_splice_write+0x18b/0xbe0 fs/splice.c:696
       do_splice_from fs/splice.c:847 [inline]
       do_splice+0x70a/0x1420 fs/splice.c:1154
       __do_sys_splice fs/splice.c:1424 [inline]
       __se_sys_splice fs/splice.c:1404 [inline]
       __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404
       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:

Chain exists of:
  &pipe->mutex/1 --> &ovl_i_mutex_dir_key[depth] --> sb_writers#5

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#5);
                               lock(&ovl_i_mutex_dir_key[depth]);
                               lock(sb_writers#5);
  lock(&pipe->mutex/1);

 *** DEADLOCK ***

1 lock held by syz-executor.0/6771:
 #0: 0000000041406b3c (sb_writers#5){.+.+}, at: file_start_write include/linux/fs.h:2825 [inline]
 #0: 0000000041406b3c (sb_writers#5){.+.+}, at: do_splice+0xe23/0x1420 fs/splice.c:1153

stack backtrace:
CPU: 1 PID: 6771 Comm: syz-executor.0 Not tainted 5.1.0-rc5+ #78
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:1571
 check_prev_add.constprop.0+0xf11/0x23c0 kernel/locking/lockdep.c:2220
 check_prevs_add kernel/locking/lockdep.c:2333 [inline]
 validate_chain kernel/locking/lockdep.c:2714 [inline]
 __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3701
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
 __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_nested fs/pipe.c:62 [inline]
 pipe_lock+0x6e/0x80 fs/pipe.c:70
 iter_file_splice_write+0x18b/0xbe0 fs/splice.c:696
 do_splice_from fs/splice.c:847 [inline]
 do_splice+0x70a/0x1420 fs/splice.c:1154
 __do_sys_splice fs/splice.c:1424 [inline]
 __se_sys_splice fs/splice.c:1404 [inline]
 __x64_sys_splice+0x2c6/0x330 fs/splice.c:1404
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458c29
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:00007f3a57911c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000458c29
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 000000000073bf00 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f3a579126d4
R13: 00000000004c7d06 R14: 00000000004dd340 R15: 00000000ffffffff

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci-upstream-kasan-gce-smack-root	2019/04/21 15:01	upstream	9e5de623	b0e8efcb	.config	log	report	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-selinux-root	2019/04/17 19:30	upstream	fe5cdef2	b0e8efcb	.config	log	report	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk
ci-upstream-kasan-gce-root	2019/02/08 19:03	upstream	74e96711	fa6c7b70	.config	log	report	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk