syzbot


possible deadlock in ext4_move_extents

Status: upstream: reported on 2022/11/05 16:08
Reported-by: syzbot+1fec0eebb32ecfda77fd@syzkaller.appspotmail.com
First crash: 21d, last: 3d20h

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc6-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/384 is trying to acquire lock:
ffff8880714ddcd0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: ext4_move_extents+0x37b/0xe70 fs/ext4/move_extent.c:610

but task is already holding lock:
ffff8880714da0a0 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ei->i_data_sem/2){++++}-{3:3}:
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
       down_read+0x39/0x50 kernel/locking/rwsem.c:1509
       ext4_map_blocks+0x398/0x1cc0 fs/ext4/inode.c:568
       ext4_getblk+0x1b9/0x770 fs/ext4/inode.c:858
       ext4_bread+0x2a/0x170 fs/ext4/inode.c:914
       ext4_quota_write+0x225/0x570 fs/ext4/super.c:7082
       write_blk fs/quota/quota_tree.c:64 [inline]
       get_free_dqblk+0x34a/0x6d0 fs/quota/quota_tree.c:130
       do_insert_tree+0x271/0x1b50 fs/quota/quota_tree.c:340
       do_insert_tree+0x744/0x1b50 fs/quota/quota_tree.c:375
       do_insert_tree+0x744/0x1b50 fs/quota/quota_tree.c:375
       do_insert_tree+0x744/0x1b50 fs/quota/quota_tree.c:375
       dq_insert_tree fs/quota/quota_tree.c:401 [inline]
       qtree_write_dquot+0x3b6/0x530 fs/quota/quota_tree.c:420
       v2_write_dquot+0x11b/0x190 fs/quota/quota_v2.c:358
       dquot_acquire+0x348/0x670 fs/quota/dquot.c:444
       ext4_acquire_dquot+0x2e0/0x400 fs/ext4/super.c:6738
       dqget+0x999/0xdc0 fs/quota/dquot.c:914
       dquot_transfer+0x612/0x870 fs/quota/dquot.c:2117
       ext4_setattr+0xb39/0x18d0 fs/ext4/inode.c:5401
       notify_change+0xe38/0x10f0 fs/attr.c:420
       chown_common+0x586/0x8f0 fs/open.c:736
       do_fchownat+0x165/0x240 fs/open.c:767
       __do_sys_chown fs/open.c:787 [inline]
       __se_sys_chown fs/open.c:785 [inline]
       __x64_sys_chown+0x7e/0x90 fs/open.c:785
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
       down_read+0x39/0x50 kernel/locking/rwsem.c:1509
       v2_read_dquot+0x4a/0x100 fs/quota/quota_v2.c:332
       dquot_acquire+0x186/0x670 fs/quota/dquot.c:435
       ext4_acquire_dquot+0x2e0/0x400 fs/ext4/super.c:6738
       dqget+0x999/0xdc0 fs/quota/dquot.c:914
       __dquot_initialize+0x291/0xcf0 fs/quota/dquot.c:1492
       ext4_create+0xb0/0x560 fs/ext4/namei.c:2802
       lookup_open fs/namei.c:3413 [inline]
       open_last_lookups fs/namei.c:3481 [inline]
       path_openat+0x12d0/0x2df0 fs/namei.c:3710
       do_filp_open+0x264/0x4f0 fs/namei.c:3740
       do_sys_openat2+0x124/0x4e0 fs/open.c:1310
       do_sys_open fs/open.c:1326 [inline]
       __do_sys_openat fs/open.c:1342 [inline]
       __se_sys_openat fs/open.c:1337 [inline]
       __x64_sys_openat+0x243/0x290 fs/open.c:1337
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
       __mutex_lock_common+0x1bd/0x26e0 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:799
       dquot_commit+0x58/0x4e0 fs/quota/dquot.c:479
       ext4_write_dquot+0x1e4/0x2b0 fs/ext4/super.c:6722
       mark_dquot_dirty fs/quota/dquot.c:346 [inline]
       mark_all_dquot_dirty fs/quota/dquot.c:384 [inline]
       __dquot_alloc_space+0xa09/0x1030 fs/quota/dquot.c:1722
       dquot_alloc_space_nodirty include/linux/quotaops.h:300 [inline]
       dquot_alloc_space include/linux/quotaops.h:313 [inline]
       swap_inode_boot_loader fs/ext4/ioctl.c:492 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1416 [inline]
       ext4_ioctl+0x4f3a/0x5430 fs/ext4/ioctl.c:1606
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&ei->i_data_sem/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3097 [inline]
       check_prevs_add kernel/locking/lockdep.c:3216 [inline]
       validate_chain+0x1898/0x6ae0 kernel/locking/lockdep.c:3831
       __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055
       lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
       down_write_nested+0xa2/0x280 kernel/locking/rwsem.c:1672
       ext4_move_extents+0x37b/0xe70 fs/ext4/move_extent.c:610
       __ext4_ioctl fs/ext4/ioctl.c:1350 [inline]
       ext4_ioctl+0x36ed/0x5430 fs/ext4/ioctl.c:1606
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
  &ei->i_data_sem/1 --> &s->s_dquot.dqio_sem --> &ei->i_data_sem/2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->i_data_sem/2);
                               lock(&s->s_dquot.dqio_sem);
                               lock(&ei->i_data_sem/2);
  lock(&ei->i_data_sem/1);

 *** DEADLOCK ***

4 locks held by syz-executor.3/384:
 #0: ffff88807f002460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:437
 #1: ffff8880714da218 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
 #1: ffff8880714da218 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: lock_two_nondirectories+0xdd/0x130 fs/inode.c:1121
 #2: ffff8880714dde48 (&sb->s_type->i_mutex_key#8/4){+.+.}-{3:3}, at: ext4_move_extents+0x360/0xe70 fs/ext4/move_extent.c:603
 #3: ffff8880714da0a0 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40

stack backtrace:
CPU: 0 PID: 384 Comm: syz-executor.3 Not tainted 6.1.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2177
 check_prev_add kernel/locking/lockdep.c:3097 [inline]
 check_prevs_add kernel/locking/lockdep.c:3216 [inline]
 validate_chain+0x1898/0x6ae0 kernel/locking/lockdep.c:3831
 __lock_acquire+0x1292/0x1f60 kernel/locking/lockdep.c:5055
 lock_acquire+0x182/0x3c0 kernel/locking/lockdep.c:5668
 down_write_nested+0xa2/0x280 kernel/locking/rwsem.c:1672
 ext4_move_extents+0x37b/0xe70 fs/ext4/move_extent.c:610
 __ext4_ioctl fs/ext4/ioctl.c:1350 [inline]
 ext4_ioctl+0x36ed/0x5430 fs/ext4/ioctl.c:1606
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f1c72a8c189
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1c73876168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1c72babf80 RCX: 00007f1c72a8c189
RDX: 0000000020000200 RSI: 00000000c028660f RDI: 0000000000000003
RBP: 00007f1c72ae7b01 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcc753e93f R14: 00007f1c73876300 R15: 0000000000022000
 </TASK>

Crashes (5):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-upstream-fs 2022/11/23 05:58 upstream eb7081409f94 9da37ae8 .config log report info possible deadlock in ext4_move_extents
ci2-upstream-fs 2022/11/19 04:15 upstream ab290eaddc4c 5bb70014 .config log report info possible deadlock in ext4_move_extents
ci2-upstream-fs 2022/11/10 18:27 upstream 1767a722a708 3ead01ad .config log report info possible deadlock in ext4_move_extents
ci2-upstream-fs 2022/11/08 14:09 upstream 59f2f4b8a757 060f945e .config log report info possible deadlock in ext4_move_extents
ci2-upstream-fs 2022/11/05 13:25 upstream 64c3dd0b98f5 6d752409 .config log report info possible deadlock in ext4_move_extents
* Struck through repros no longer work on HEAD.