syzbot


possible deadlock in md_open
Status: fixed on 2022/03/08 16:11
Reported-by: syzbot+fadc0aaf497e6a493b9f@syzkaller.appspotmail.com
Fix commit: 7df835a32a8b md: fix a lock order reversal in md_alloc
First crash: 273d, last: 240d

Cause bisection: introduced by (bisect log) [merge commit]:
commit 3f3b83f314cb2eef140162e98c26239550ba013f
Author: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Tue Aug 24 02:23:18 2021 +0000

  Merge remote-tracking branch 'block/for-next'

Crash: possible deadlock in md_open (log)
Repro: C syz .config
Patch testing requests:
Created Duration User Patch Repo Result
2021/08/30 12:07 21m hch@infradead.org patch git://git.kernel.dk/linux-block for-next OK
2021/08/29 13:22 10m phind.uet@gmail.com linux-next report log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
5.15.0-rc2-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor142/6549 is trying to acquire lock:
ffff88801b27c230 (&mddev->open_mutex){+.+.}-{3:3}, at: md_open+0xfd/0x2e0 drivers/md/md.c:7815

but task is already holding lock:
ffff888076d7b918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x9b/0xb60 block/bdev.c:816

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&disk->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       bd_register_pending_holders+0x2c/0x470 block/holder.c:160
       device_add_disk+0x74c/0xfc0 block/genhd.c:475
       add_disk include/linux/genhd.h:221 [inline]
       md_alloc+0x91d/0x1150 drivers/md/md.c:5707
       md_probe+0x69/0x70 drivers/md/md.c:5738
       blk_request_module+0x111/0x1d0 block/genhd.c:637
       blkdev_get_no_open+0x178/0x1e0 block/bdev.c:739
       blkdev_get_by_dev.part.0+0x22/0xb60 block/bdev.c:803
       blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
       swsusp_check+0x4d/0x270 kernel/power/swap.c:1525
       software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:977
       software_resume kernel/power/hibernate.c:86 [inline]
       resume_store+0x161/0x190 kernel/power/hibernate.c:1179
       kobj_attr_store+0x50/0x80 lib/kobject.c:856
       sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2163 [inline]
       new_sync_write+0x429/0x660 fs/read_write.c:507
       vfs_write+0x7cf/0xae0 fs/read_write.c:594
       ksys_write+0x12d/0x250 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&mddev->open_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3051 [inline]
       check_prevs_add kernel/locking/lockdep.c:3174 [inline]
       validate_chain kernel/locking/lockdep.c:3789 [inline]
       __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
       lock_acquire kernel/locking/lockdep.c:5625 [inline]
       lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
       __mutex_lock_common kernel/locking/mutex.c:596 [inline]
       __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
       md_open+0xfd/0x2e0 drivers/md/md.c:7815
       blkdev_get_whole+0x99/0x2a0 block/bdev.c:668
       blkdev_get_by_dev.part.0+0x354/0xb60 block/bdev.c:823
       blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
       swsusp_check+0x4d/0x270 kernel/power/swap.c:1525
       software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:977
       software_resume kernel/power/hibernate.c:86 [inline]
       resume_store+0x161/0x190 kernel/power/hibernate.c:1179
       kobj_attr_store+0x50/0x80 lib/kobject.c:856
       sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
       kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
       call_write_iter include/linux/fs.h:2163 [inline]
       new_sync_write+0x429/0x660 fs/read_write.c:507
       vfs_write+0x7cf/0xae0 fs/read_write.c:594
       ksys_write+0x12d/0x250 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&disk->open_mutex);
                               lock(&mddev->open_mutex);
                               lock(&disk->open_mutex);
  lock(&mddev->open_mutex);

 *** DEADLOCK ***

5 locks held by syz-executor142/6549:
 #0: ffff888026af8460 (sb_writers#6){.+.+}-{0:0}, at: ksys_write+0x12d/0x250 fs/read_write.c:647
 #1: ffff888024d5e488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x287/0x500 fs/kernfs/file.c:287
 #2: ffff8881441fe830 (kn->active#90){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ab/0x500 fs/kernfs/file.c:288
 #3: ffffffff8b84fe28 (system_transition_mutex/1){+.+.}-{3:3}, at: software_resume.part.0+0x19/0x1f0 kernel/power/hibernate.c:932
 #4: ffff888076d7b918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev.part.0+0x9b/0xb60 block/bdev.c:816

stack backtrace:
CPU: 0 PID: 6549 Comm: syz-executor142 Not tainted 5.15.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131
 check_prev_add kernel/locking/lockdep.c:3051 [inline]
 check_prevs_add kernel/locking/lockdep.c:3174 [inline]
 validate_chain kernel/locking/lockdep.c:3789 [inline]
 __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015
 lock_acquire kernel/locking/lockdep.c:5625 [inline]
 lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590
 __mutex_lock_common kernel/locking/mutex.c:596 [inline]
 __mutex_lock+0x131/0x12f0 kernel/locking/mutex.c:729
 md_open+0xfd/0x2e0 drivers/md/md.c:7815
 blkdev_get_whole+0x99/0x2a0 block/bdev.c:668
 blkdev_get_by_dev.part.0+0x354/0xb60 block/bdev.c:823
 blkdev_get_by_dev+0x6b/0x80 block/bdev.c:856
 swsusp_check+0x4d/0x270 kernel/power/swap.c:1525
 software_resume.part.0+0x102/0x1f0 kernel/power/hibernate.c:977
 software_resume kernel/power/hibernate.c:86 [inline]
 resume_store+0x161/0x190 kernel/power/hibernate.c:1179
 kobj_attr_store+0x50/0x80 lib/kobject.c:856
 sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:139
 kernfs_fop_write_iter+0x342/0x500 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2163 [inline]
 new_sync_write+0x429/0x660 fs/read_write.c:507
 vfs_write+0x7cf/0xae0 fs/read_write.c:594
 ksys_write+0x12d/0x250 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7efe727d1279
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff6361fb08 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffff

Crashes (2844):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce 2021/09/21 04:21 upstream e8f71f89236e af796c18 .config log report syz C possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/15 14:23 upstream 3ca706c189db 07e953c1 .config log report syz C possible deadlock in md_open
ci-upstream-linux-next-kasan-gce-root 2021/09/05 07:04 linux-next c1b13fe76e95 d236a457 .config log report syz C possible deadlock in md_open
ci-upstream-linux-next-kasan-gce-root 2021/08/24 13:49 linux-next 372b2891c15a b599f2fc .config log report syz C possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/26 10:21 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/26 09:11 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/26 08:08 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/26 06:26 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/26 02:30 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-selinux-root 2021/09/26 01:15 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/26 00:05 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 23:43 upstream a5e0aceabef6 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 21:09 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 20:00 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 17:23 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 16:13 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 14:15 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/25 12:21 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/25 12:13 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 11:12 upstream 7d42e9818258 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 09:57 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/25 08:28 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 06:29 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 04:54 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 02:00 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/25 00:42 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 23:03 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 21:52 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 20:46 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 19:43 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 19:40 upstream 4c4f0c2bf341 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 18:29 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 16:01 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 10:37 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 07:46 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 05:07 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 04:14 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 02:56 upstream f9e36107ec70 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 01:56 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/24 00:39 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 23:28 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 21:01 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-smack-root 2021/09/23 16:55 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 15:44 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-root 2021/09/23 14:39 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 13:47 upstream 58e2cf5d7946 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 11:06 upstream cf1d2c3e7e2f 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 09:36 upstream cf1d2c3e7e2f 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce 2021/09/23 06:26 upstream cf1d2c3e7e2f 8cac236e .config log report info possible deadlock in md_open
ci-upstream-kasan-gce-386 2021/09/09 00:37 upstream 0f4b9289bad3 e2776ee4 .config log report info possible deadlock in md_open
ci-upstream-linux-next-kasan-gce-root 2021/09/23 02:38 linux-next e90f9946ba28 8cac236e .config log report info possible deadlock in md_open
ci-upstream-linux-next-kasan-gce-root 2021/08/24 11:05 linux-next 372b2891c15a b599f2fc .config log report info possible deadlock in md_open