syzbot


possible deadlock in blkdev_put (4)

Status: auto-obsoleted due to no activity on 2024/02/07 19:21
Subsystems: block
[Documentation on labels]
Reported-by: syzbot+0c538bd7f64c3c6e9a3c@syzkaller.appspotmail.com
First crash: 246d, last: 228d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [block?] possible deadlock in blkdev_put (4) 1 (2) 2024/03/13 10:29
Similar bugs (5)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 possible deadlock in blkdev_put btrfs C error 2 501d 530d 0/1 upstream: reported C repro on 2023/01/01 16:48
upstream possible deadlock in blkdev_put btrfs 1 1363d 1363d 0/27 auto-closed as invalid on 2021/01/18 22:03
upstream possible deadlock in blkdev_put (3) block C 870 753d 825d 22/27 fixed on 2023/02/24 13:50
upstream possible deadlock in blkdev_put (2) block C done 502 829d 931d 20/27 fixed on 2022/03/08 16:11
linux-4.14 possible deadlock in blkdev_put C 5 481d 1353d 0/1 upstream: reported C repro on 2020/10/01 09:27

Sample crash report:
syz-executor.5: attempt to access beyond end of device
loop162: rw=0, sector=0, nr_sectors = 8 limit=0
EXT4-fs (loop5): couldn't read superblock of external journal
======================================================
WARNING: possible circular locking dependency detected
6.6.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/7135 is trying to acquire lock:
ffff888076dcf4c8 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xff/0x770 block/bdev.c:884

but task is already holding lock:
ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_get_journal_blkdev fs/ext4/super.c:5861 [inline]
ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_open_dev_journal fs/ext4/super.c:5933 [inline]
ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_journal fs/ext4/super.c:5996 [inline]
ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_and_init_journal+0x30f/0x2550 fs/ext4/super.c:4906

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&type->s_umount_key#31){++++}-{3:3}:
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1520
       __super_lock fs/super.c:58 [inline]
       super_lock+0x176/0x390 fs/super.c:117
       super_lock_shared fs/super.c:146 [inline]
       super_lock_shared_active fs/super.c:1431 [inline]
       fs_bdev_sync+0xa5/0x170 fs/super.c:1466
       blkdev_flushbuf block/ioctl.c:372 [inline]
       blkdev_common_ioctl+0x889/0x2860 block/ioctl.c:502
       blkdev_ioctl+0x520/0x730 block/ioctl.c:624
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:871 [inline]
       __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:857
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (&bdev->bd_holder_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x136/0xd60 kernel/locking/mutex.c:747
       bdev_mark_dead+0x32/0x1a0 block/bdev.c:961
       disk_force_media_change+0x145/0x1c0 block/disk-events.c:302
       __loop_clr_fd+0x3df/0x690 drivers/block/loop.c:1174
       blkdev_put+0x5d2/0x770
       deactivate_locked_super+0xa4/0x110 fs/super.c:481
       cleanup_mnt+0x426/0x4c0 fs/namespace.c:1254
       task_work_run+0x24a/0x300 kernel/task_work.c:180
       resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
       exit_to_user_mode_loop+0xde/0x100 kernel/entry/common.c:171
       exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
       __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
       syscall_exit_to_user_mode+0x64/0x280 kernel/entry/common.c:296
       do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&disk->open_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5136
       lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5753
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x136/0xd60 kernel/locking/mutex.c:747
       blkdev_put+0xff/0x770 block/bdev.c:884
       ext4_get_journal_blkdev fs/ext4/super.c:5920 [inline]
       ext4_open_dev_journal fs/ext4/super.c:5933 [inline]
       ext4_load_journal fs/ext4/super.c:5996 [inline]
       ext4_load_and_init_journal+0xc26/0x2550 fs/ext4/super.c:4906
       __ext4_fill_super fs/ext4/super.c:5374 [inline]
       ext4_fill_super+0x4863/0x6d10 fs/ext4/super.c:5703
       get_tree_bdev+0x416/0x5b0 fs/super.c:1577
       vfs_get_tree+0x8c/0x280 fs/super.c:1750
       do_new_mount+0x28f/0xae0 fs/namespace.c:3335
       do_mount fs/namespace.c:3675 [inline]
       __do_sys_mount fs/namespace.c:3884 [inline]
       __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3861
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
  &disk->open_mutex --> &bdev->bd_holder_lock --> &type->s_umount_key#31

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&type->s_umount_key#31);
                               lock(&bdev->bd_holder_lock);
                               lock(&type->s_umount_key#31);
  lock(&disk->open_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.5/7135:
 #0: ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_get_journal_blkdev fs/ext4/super.c:5861 [inline]
 #0: ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_open_dev_journal fs/ext4/super.c:5933 [inline]
 #0: ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_journal fs/ext4/super.c:5996 [inline]
 #0: ffff88803524e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: ext4_load_and_init_journal+0x30f/0x2550 fs/ext4/super.c:4906

stack backtrace:
CPU: 1 PID: 7135 Comm: syz-executor.5 Not tainted 6.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x375/0x4a0 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 kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5136
 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5753
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x136/0xd60 kernel/locking/mutex.c:747
 blkdev_put+0xff/0x770 block/bdev.c:884
 ext4_get_journal_blkdev fs/ext4/super.c:5920 [inline]
 ext4_open_dev_journal fs/ext4/super.c:5933 [inline]
 ext4_load_journal fs/ext4/super.c:5996 [inline]
 ext4_load_and_init_journal+0xc26/0x2550 fs/ext4/super.c:4906
 __ext4_fill_super fs/ext4/super.c:5374 [inline]
 ext4_fill_super+0x4863/0x6d10 fs/ext4/super.c:5703
 get_tree_bdev+0x416/0x5b0 fs/super.c:1577
 vfs_get_tree+0x8c/0x280 fs/super.c:1750
 do_new_mount+0x28f/0xae0 fs/namespace.c:3335
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fcf7567e1ea
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 09 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fcf762f4ee8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fcf762f4f80 RCX: 00007fcf7567e1ea
RDX: 0000000020000040 RSI: 0000000020000500 RDI: 00007fcf762f4f40
RBP: 0000000020000040 R08: 00007fcf762f4f80 R09: 0000000001400009
R10: 0000000001400009 R11: 0000000000000202 R12: 0000000020000500
R13: 00007fcf762f4f40 R14: 00000000000004d2 R15: 000000000000002c
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/10/30 19:21 upstream ffc253263a13 b5729d82 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in blkdev_put
2023/10/12 21:50 upstream 401644852d0b fc170927 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root possible deadlock in blkdev_put
* Struck through repros no longer work on HEAD.