syzbot


possible deadlock in seq_read_iter (3)

Status: upstream: reported on 2024/02/12 10:36
Subsystems: overlayfs
[Documentation on labels]
Reported-by: syzbot+af9aa785e14a67796a87@syzkaller.appspotmail.com
Fix commit: 16b52bbee482 kernfs: annotate different lockdep class for of->mutex of writable files
Patched on: [ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci2-upstream-fs ci2-upstream-kcsan-gce], missing on: [ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-net-next-test-gce ci2-upstream-usb]
First crash: 64d, last: 1d08h
Duplicate bugs (2)
duplicates (2):
Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
possible deadlock in iter_file_splice_write (3) overlayfs 22 1d12h 33d 0/26 closed as dup on 2024/03/14 09:27
possible deadlock in kernfs_fop_llseek kernfs C done 38 1d11h 13d 18/26 closed as dup on 2024/04/07 11:03
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [overlayfs?] possible deadlock in seq_read_iter (3) 1 (2) 2024/03/13 12:30
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in seq_read_iter (2) overlayfs C done done 14 112d 272d 26/26 fixed on 2024/02/02 10:05
upstream possible deadlock in seq_read_iter fs 2 983d 989d 0/26 auto-closed as invalid on 2021/12/05 03:01

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
syz-executor.4/8163 is trying to acquire lock:
ffff8880649d00a0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb7/0xd60 fs/seq_file.c:182

but task is already holding lock:
ffff88807b2af468 (&pipe->mutex){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&pipe->mutex){+.+.}-{3:3}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd77/0x1880 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #4 (sb_writers#4){.+.+}-{0:0}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1662 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1798
       mnt_want_write+0x3f/0x90 fs/namespace.c:409
       ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629
       lookup_open fs/namei.c:3497 [inline]
       open_last_lookups fs/namei.c:3566 [inline]
       path_openat+0x1425/0x3240 fs/namei.c:3796
       do_filp_open+0x235/0x490 fs/namei.c:3826
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
       do_sys_open fs/open.c:1421 [inline]
       __do_sys_openat fs/open.c:1437 [inline]
       __se_sys_openat fs/open.c:1432 [inline]
       __x64_sys_openat+0x247/0x2a0 fs/open.c:1432
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #3 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:803 [inline]
       lookup_slow fs/namei.c:1708 [inline]
       lookup_one_unlocked+0x197/0x290 fs/namei.c:2817
       ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
       ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
       ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
       ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
       lookup_open fs/namei.c:3475 [inline]
       open_last_lookups fs/namei.c:3566 [inline]
       path_openat+0x1033/0x3240 fs/namei.c:3796
       do_filp_open+0x235/0x490 fs/namei.c:3826
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
       do_sys_open fs/open.c:1421 [inline]
       __do_sys_open fs/open.c:1429 [inline]
       __se_sys_open fs/open.c:1425 [inline]
       __x64_sys_open+0x225/0x270 fs/open.c:1425
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #2 (&ovl_i_mutex_dir_key[depth]#2){.+.+}-{3:3}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:803 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1708
       walk_component+0x2e1/0x410 fs/namei.c:2004
       lookup_last fs/namei.c:2461 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2485
       filename_lookup+0x256/0x610 fs/namei.c:2514
       kern_path+0x35/0x50 fs/namei.c:2622
       lookup_bdev+0xc5/0x290 block/bdev.c:1072
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334
       call_write_iter include/linux/fs.h:2108 [inline]
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0xa84/0xcb0 fs/read_write.c:590
       ksys_write+0x1a0/0x2c0 fs/read_write.c:643
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #1 (&of->mutex){+.+.}-{3:3}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
       seq_read_iter+0x3d0/0xd60 fs/seq_file.c:225
       call_read_iter include/linux/fs.h:2102 [inline]
       new_sync_read fs/read_write.c:395 [inline]
       vfs_read+0x97b/0xb70 fs/read_write.c:476
       ksys_read+0x1a0/0x2c0 fs/read_write.c:619
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #0 (&p->lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
       call_read_iter include/linux/fs.h:2102 [inline]
       copy_splice_read+0x662/0xb60 fs/splice.c:365
       do_splice_read fs/splice.c:985 [inline]
       splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
       do_sendfile+0x515/0xdc0 fs/read_write.c:1301
       __do_sys_sendfile64 fs/read_write.c:1362 [inline]
       __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

other info that might help us debug this:

Chain exists of:
  &p->lock --> sb_writers#4 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#4);
                               lock(&pipe->mutex);
  lock(&p->lock);

 *** DEADLOCK ***

1 lock held by syz-executor.4/8163:
 #0: ffff88807b2af468 (&pipe->mutex){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292

stack backtrace:
CPU: 1 PID: 8163 Comm: syz-executor.4 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
 call_read_iter include/linux/fs.h:2102 [inline]
 copy_splice_read+0x662/0xb60 fs/splice.c:365
 do_splice_read fs/splice.c:985 [inline]
 splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
 do_sendfile+0x515/0xdc0 fs/read_write.c:1301
 __do_sys_sendfile64 fs/read_write.c:1362 [inline]
 __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f872827de69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8727dff0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f87283ac050 RCX: 00007f872827de69
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000003
RBP: 00007f87282ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f87283ac050 R15: 00007fff2911b388
 </TASK>

Crashes (144):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/04/15 12:12 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/15 10:03 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/15 08:19 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/15 06:31 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/15 03:35 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/15 01:00 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/14 20:35 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/14 13:04 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/14 12:00 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/14 09:53 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/14 05:40 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 23:39 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 11:32 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 09:51 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 08:22 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 06:39 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 02:21 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/13 00:48 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 23:30 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 13:55 upstream fe46a7dd189e 27de0a5c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 08:40 upstream fe46a7dd189e 27de0a5c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 07:08 upstream fe46a7dd189e 27de0a5c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 05:04 upstream fe46a7dd189e 27de0a5c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 04:01 upstream fe46a7dd189e 27de0a5c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 01:34 upstream fe46a7dd189e 95ed9ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/12 00:16 upstream fe46a7dd189e 95ed9ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/11 12:11 upstream fe46a7dd189e 33b9e058 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 23:45 upstream fe46a7dd189e 4320ec32 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 21:24 upstream fe46a7dd189e 4320ec32 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 20:03 upstream fe46a7dd189e 4320ec32 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 16:31 upstream fe46a7dd189e 4320ec32 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 10:54 upstream fe46a7dd189e 171ec371 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 09:47 upstream fe46a7dd189e 171ec371 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 08:36 upstream fe46a7dd189e 171ec371 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 03:31 upstream fe46a7dd189e 171ec371 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/10 01:40 upstream fe46a7dd189e 171ec371 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/09 12:50 upstream fe46a7dd189e f3234354 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/09 09:06 upstream fe46a7dd189e f3234354 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/08 23:04 upstream fe46a7dd189e 53df08b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/08 19:56 upstream fe46a7dd189e 53df08b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/08 16:26 upstream fe46a7dd189e 53df08b6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/08 12:21 upstream fe46a7dd189e ca620dd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/07 19:24 upstream fe46a7dd189e ca620dd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/04/07 16:30 upstream fe46a7dd189e ca620dd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
2024/02/12 02:37 upstream 841c35169323 77b23aa1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in seq_read_iter
* Struck through repros no longer work on HEAD.