possible deadlock in swap_inode_boot_loader (3)

Status: upstream: reported on 2026/10/23 21:33
Reported-by: syzbot+abd1d5e0c10804581255@syzkaller.appspotmail.com
First crash: 1d17h, last: 1d17h
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in swap_inode_boot_loader 4 8 383d 521d 0/3 auto-obsoleted due to no activity on 2026/01/15 12:57
linux-5.15 possible deadlock in swap_inode_boot_loader origin:lts-only 4 syz, C error 13 38d 536d 0/3 upstream: reported C repro on 2025/05/06 21:29
linux-6.1 possible deadlock in swap_inode_boot_loader (2) 4 3 163d 243d 0/3 auto-obsoleted due to no activity on 2026/08/22 22:56

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G        W         
------------------------------------------------------
syz.3.10064/4387 is trying to acquire lock:
ffff888074b0f0e0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: swap_inode_boot_loader+0x571/0x10f0 fs/ext4/ioctl.c:426

but task is already holding lock:
ffff888074b08288 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ei->i_data_sem/2){++++}-{3:3}:
       down_write+0x36/0x60 kernel/locking/rwsem.c:1573
       ext4_map_blocks+0x914/0x1a90 fs/ext4/inode.c:674
       ext4_getblk+0x1c5/0x720 fs/ext4/inode.c:892
       ext4_bread+0x26/0x170 fs/ext4/inode.c:948
       ext4_quota_write+0x237/0x580 fs/ext4/super.c:7228
       write_blk fs/quota/quota_tree.c:70 [inline]
       find_free_dqentry+0x68c/0xc30 fs/quota/quota_tree.c:318
       do_insert_tree+0x717/0x1060 fs/quota/quota_tree.c:400
       do_insert_tree+0x9f5/0x1060 fs/quota/quota_tree.c:402
       do_insert_tree+0x9f5/0x1060 fs/quota/quota_tree.c:402
       do_insert_tree+0x9f5/0x1060 fs/quota/quota_tree.c:402
       dq_insert_tree fs/quota/quota_tree.c:432 [inline]
       qtree_write_dquot+0x49b/0x5d0 fs/quota/quota_tree.c:451
       v2_write_dquot+0x108/0x190 fs/quota/quota_v2.c:361
       dquot_acquire+0x2d5/0x520 fs/quota/dquot.c:500
       ext4_acquire_dquot+0x2e3/0x4a0 fs/ext4/super.c:6837
       dqget+0x713/0xbb0 fs/quota/dquot.c:1013
       __dquot_initialize+0x3a9/0xd00 fs/quota/dquot.c:1542
       ext4_process_orphan+0x4c/0x2e0 fs/ext4/orphan.c:327
       ext4_orphan_cleanup+0xdfe/0x1650 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5574 [inline]
       ext4_fill_super+0x6f0c/0x78f0 fs/ext4/super.c:5693
       get_tree_bdev+0x3e6/0x610 fs/super.c:1377
       vfs_get_tree+0x88/0x270 fs/super.c:1584
       do_new_mount+0x247/0xa40 fs/namespace.c:3078
       do_mount fs/namespace.c:3421 [inline]
       __do_sys_mount fs/namespace.c:3629 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       v2_read_dquot+0x4a/0x110 fs/quota/quota_v2.c:335
       dquot_acquire+0x152/0x520 fs/quota/dquot.c:491
       ext4_acquire_dquot+0x2e3/0x4a0 fs/ext4/super.c:6837
       dqget+0x713/0xbb0 fs/quota/dquot.c:1013
       __dquot_initialize+0x3a9/0xd00 fs/quota/dquot.c:1542
       ext4_process_orphan+0x4c/0x2e0 fs/ext4/orphan.c:327
       ext4_orphan_cleanup+0xdfe/0x1650 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5574 [inline]
       ext4_fill_super+0x6f0c/0x78f0 fs/ext4/super.c:5693
       get_tree_bdev+0x3e6/0x610 fs/super.c:1377
       vfs_get_tree+0x88/0x270 fs/super.c:1584
       do_new_mount+0x247/0xa40 fs/namespace.c:3078
       do_mount fs/namespace.c:3421 [inline]
       __do_sys_mount fs/namespace.c:3629 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       dquot_commit+0x5a/0x410 fs/quota/dquot.c:535
       ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6817
       mark_dquot_dirty fs/quota/dquot.c:400 [inline]
       mark_all_dquot_dirty+0x1e3/0x400 fs/quota/dquot.c:440
       __dquot_alloc_space+0x5f6/0xe50 fs/quota/dquot.c:1777
       dquot_alloc_space_nodirty include/linux/quotaops.h:293 [inline]
       dquot_alloc_space include/linux/quotaops.h:306 [inline]
       dquot_alloc_block include/linux/quotaops.h:330 [inline]
       ext4_mb_new_blocks+0xf55/0x44d0 fs/ext4/mballoc.c:5740
       ext4_new_meta_blocks+0x172/0x3d0 fs/ext4/balloc.c:739
       ext4_ext_grow_indepth fs/ext4/extents.c:1331 [inline]
       ext4_ext_create_new_leaf fs/ext4/extents.c:1437 [inline]
       ext4_ext_insert_extent+0x101d/0x47d0 fs/ext4/extents.c:2120
       ext4_split_extent_at+0x7c4/0xf80 fs/ext4/extents.c:3254
       ext4_force_split_extent_at fs/ext4/extents.c:338 [inline]
       ext4_swap_extents+0x1145/0x1d60 fs/ext4/extents.c:5795
       move_extent_per_page+0x1f9b/0x48e0 fs/ext4/move_extent.c:367
       ext4_move_extents+0x8e1/0xbe0 fs/ext4/move_extent.c:678
       __ext4_ioctl fs/ext4/ioctl.c:1367 [inline]
       ext4_ioctl+0x37d6/0x4120 fs/ext4/ioctl.c:1623
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&ei->i_data_sem/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3162 [inline]
       check_prevs_add kernel/locking/lockdep.c:3281 [inline]
       validate_chain kernel/locking/lockdep.c:3897 [inline]
       __lock_acquire+0x3a03/0x7ea0 kernel/locking/lockdep.c:5171
       lock_acquire+0x1bc/0x4a0 kernel/locking/lockdep.c:5790
       down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
       swap_inode_boot_loader+0x571/0x10f0 fs/ext4/ioctl.c:426
       __ext4_ioctl fs/ext4/ioctl.c:1433 [inline]
       ext4_ioctl+0x1e66/0x4120 fs/ext4/ioctl.c:1623
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

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 ***

5 locks held by syz.3.10064/4387:
 #0: ffff888057f06460 (sb_writers#4){++++}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:446
 #1: ffff888074b08400 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline]
 #1: ffff888074b08400 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: lock_two_nondirectories+0xf7/0x150 fs/inode.c:1208
 #2: ffff888074b0f258 (&sb->s_type->i_mutex_key#9/4){+.+.}-{3:3}, at: swap_inode_boot_loader+0x70/0x10f0 fs/ext4/ioctl.c:385
 #3: ffff888074b0f3f8 (mapping.invalidate_lock#2){++++}-{3:3}, at: filemap_invalidate_lock include/linux/fs.h:809 [inline]
 #3: ffff888074b0f3f8 (mapping.invalidate_lock#2){++++}-{3:3}, at: swap_inode_boot_loader+0x39f/0x10f0 fs/ext4/ioctl.c:402
 #4: ffff888074b08288 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40 fs/ext4/move_extent.c:-1

stack backtrace:
CPU: 0 PID: 4387 Comm: syz.3.10064 Tainted: G        W          syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x2f8/0x400 kernel/locking/lockdep.c:2215
 check_prev_add kernel/locking/lockdep.c:3162 [inline]
 check_prevs_add kernel/locking/lockdep.c:3281 [inline]
 validate_chain kernel/locking/lockdep.c:3897 [inline]
 __lock_acquire+0x3a03/0x7ea0 kernel/locking/lockdep.c:5171
 lock_acquire+0x1bc/0x4a0 kernel/locking/lockdep.c:5790
 down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
 swap_inode_boot_loader+0x571/0x10f0 fs/ext4/ioctl.c:426
 __ext4_ioctl fs/ext4/ioctl.c:1433 [inline]
 ext4_ioctl+0x1e66/0x4120 fs/ext4/ioctl.c:1623
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9e3e39f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9e3f230028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f9e3e625fa0 RCX: 00007f9e3e39f559
RDX: 0000000000000000 RSI: 0000000000006611 RDI: 0000000000000005
RBP: 00007f9e3e436b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9e3e626038 R14: 00007f9e3e625fa0 R15: 00007fff89efad38
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/23 21:32 linux-6.1.y 79807e970724 1d9ca40b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in swap_inode_boot_loader
* Struck through repros no longer work on HEAD.