syzbot


possible deadlock in swap_inode_boot_loader

Status: upstream: reported syz repro on 2025/05/06 21:29
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+3d141fd3857666bf45d8@syzkaller.appspotmail.com
First crash: 3d05h, last: 14h41m
Bug presence (2)
Date Name Commit Repro Result
2025/05/09 linux-5.15.y (ToT) 3b8db0e4f263 C [report] possible deadlock in swap_inode_boot_loader
2025/05/09 upstream (ToT) 9c69f8884904 C Didn't crash

Sample crash report:
ext4 filesystem being mounted at /100/file0 supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
5.15.181-syzkaller #0 Not tainted
------------------------------------------------------
syz.5.553/7904 is trying to acquire lock:
ffff888060f43e48 (&ei->i_data_sem/1){+.+.}-{3:3}, at: swap_inode_boot_loader+0x529/0x10f0 fs/ext4/ioctl.c:176

but task is already holding lock:
ffff888060f41668 (&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_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       ext4_map_blocks+0x32f/0x1b30 fs/ext4/inode.c:598
       ext4_getblk+0x16d/0x630 fs/ext4/inode.c:870
       ext4_bread+0x26/0x180 fs/ext4/inode.c:923
       ext4_quota_write+0x230/0x570 fs/ext4/super.c:6591
       write_blk fs/quota/quota_tree.c:64 [inline]
       get_free_dqblk+0x387/0x7d0 fs/quota/quota_tree.c:125
       do_insert_tree+0x214/0x1970 fs/quota/quota_tree.c:335
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       do_insert_tree+0x5b1/0x1970 fs/quota/quota_tree.c:366
       dq_insert_tree fs/quota/quota_tree.c:392 [inline]
       qtree_write_dquot+0x361/0x4b0 fs/quota/quota_tree.c:411
       v2_write_dquot+0x108/0x190 fs/quota/quota_v2.c:358
       dquot_acquire+0x2d5/0x520 fs/quota/dquot.c:472
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6200
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       __dquot_initialize+0x328/0xcb0 fs/quota/dquot.c:1517
       add_dquot_ref+0x2b4/0x380 fs/quota/dquot.c:1060
       dquot_load_quota_sb+0x875/0xac0 fs/quota/dquot.c:2475
       dquot_resume+0x330/0x860 fs/quota/dquot.c:2532
       ext4_remount+0x1a2a/0x26e0 fs/ext4/super.c:5996
       reconfigure_super+0x219/0x880 fs/super.c:938
       do_remount fs/namespace.c:2669 [inline]
       path_mount+0xd3e/0x1020 fs/namespace.c:3335
       do_mount fs/namespace.c:3356 [inline]
       __do_sys_mount fs/namespace.c:3564 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3541
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       v2_read_dquot+0x4a/0x110 fs/quota/quota_v2.c:332
       dquot_acquire+0x152/0x520 fs/quota/dquot.c:463
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6200
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       __dquot_initialize+0x328/0xcb0 fs/quota/dquot.c:1517
       add_dquot_ref+0x2b4/0x380 fs/quota/dquot.c:1060
       dquot_load_quota_sb+0x875/0xac0 fs/quota/dquot.c:2475
       dquot_resume+0x330/0x860 fs/quota/dquot.c:2532
       ext4_remount+0x1a2a/0x26e0 fs/ext4/super.c:5996
       reconfigure_super+0x219/0x880 fs/super.c:938
       do_remount fs/namespace.c:2669 [inline]
       path_mount+0xd3e/0x1020 fs/namespace.c:3335
       do_mount fs/namespace.c:3356 [inline]
       __do_sys_mount fs/namespace.c:3564 [inline]
       __se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3541
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       dquot_commit+0x5a/0x410 fs/quota/dquot.c:507
       ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6180
       mark_dquot_dirty fs/quota/dquot.c:372 [inline]
       mark_all_dquot_dirty+0xf9/0x400 fs/quota/dquot.c:412
       __dquot_free_space+0x7ca/0xb90 fs/quota/dquot.c:1942
       dquot_free_space_nodirty include/linux/quotaops.h:376 [inline]
       dquot_free_space+0x1b/0x30 include/linux/quotaops.h:381
       swap_inode_boot_loader+0xc6a/0x10f0 fs/ext4/ioctl.c:241
       __ext4_ioctl fs/ext4/ioctl.c:1056 [inline]
       ext4_ioctl+0x18d5/0x3570 fs/ext4/ioctl.c:1276
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&ei->i_data_sem/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
       swap_inode_boot_loader+0x529/0x10f0 fs/ext4/ioctl.c:176
       __ext4_ioctl fs/ext4/ioctl.c:1056 [inline]
       ext4_ioctl+0x18d5/0x3570 fs/ext4/ioctl.c:1276
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

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.5.553/7904:
 #0: ffff88805d1d6460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:421
 #1: ffff888060f417e0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #1: ffff888060f417e0 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: lock_two_nondirectories+0xd5/0x150 fs/inode.c:1147
 #2: ffff888060f43fc0 (&sb->s_type->i_mutex_key#9/4){+.+.}-{3:3}, at: swap_inode_boot_loader+0x70/0x10f0 fs/ext4/ioctl.c:135
 #3: ffff888060f44160 (mapping.invalidate_lock){++++}-{3:3}, at: filemap_invalidate_lock include/linux/fs.h:832 [inline]
 #3: ffff888060f44160 (mapping.invalidate_lock){++++}-{3:3}, at: swap_inode_boot_loader+0x37f/0x10f0 fs/ext4/ioctl.c:152
 #4: ffff888060f41668 (&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: 1 PID: 7904 Comm: syz.5.553 Not tainted 5.15.181-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 down_write_nested+0x3b/0x60 kernel/locking/rwsem.c:1667
 swap_inode_boot_loader+0x529/0x10f0 fs/ext4/ioctl.c:176
 __ext4_ioctl fs/ext4/ioctl.c:1056 [inline]
 ext4_ioctl+0x18d5/0x3570 fs/ext4/ioctl.c:1276
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f42bc1c6969
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f42bb436038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f42bc3edfa0 RCX: 00007f42bc1c6969
RDX: 0000000000000000 RSI: 0000000000006611 RDI: 0000000000000005
RBP: 00007f42bc248ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f42bc3edfa0 R15: 00007ffe3ead5018
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/07 13:04 linux-5.15.y 16fdf2c7111b 350f4ffc .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-linux-5-15-kasan possible deadlock in swap_inode_boot_loader
2025/05/06 21:28 linux-5.15.y 16fdf2c7111b 350f4ffc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in swap_inode_boot_loader
* Struck through repros no longer work on HEAD.