syzbot


possible deadlock in ext4_ioctl (4)

Status: upstream: reported on 2024/12/07 16:00
Reported-by: syzbot+080a370855693097b1d3@syzkaller.appspotmail.com
First crash: 118d, last: 32d
Similar bugs (6)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in ext4_ioctl 2 554d 653d 0/3 auto-obsoleted due to no activity on 2024/01/09 18:17
upstream possible deadlock in ext4_ioctl ext4 44 713d 907d 0/28 auto-obsoleted due to no activity on 2023/08/20 05:40
linux-5.15 possible deadlock in ext4_ioctl (2) origin:lts-only C done 14 45d 267d 0/3 upstream: reported C repro on 2024/07/11 06:29
linux-6.1 possible deadlock in ext4_ioctl (2) 1 420d 420d 0/3 auto-obsoleted due to no activity on 2024/05/18 23:21
linux-6.1 possible deadlock in ext4_ioctl (3) 2 261d 293d 0/3 auto-obsoleted due to no activity on 2024/10/25 05:49
linux-5.15 possible deadlock in ext4_ioctl 1 427d 427d 0/3 auto-obsoleted due to no activity on 2024/05/12 20:19

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.1.129-syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1680/11518 is trying to acquire lock:
ffff8880554634b0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: swap_inode_boot_loader fs/ext4/ioctl.c:426 [inline]
ffff8880554634b0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
ffff8880554634b0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: ext4_ioctl+0x461f/0x5f80 fs/ext4/ioctl.c:1614

but task is already holding lock:
ffff888055462aa8 (&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+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_read+0xad/0xa30 kernel/locking/rwsem.c:1520
       ext4_map_blocks+0x379/0x1cb0 fs/ext4/inode.c:603
       ext4_getblk+0x1eb/0x7c0 fs/ext4/inode.c:889
       ext4_bread+0x2a/0x170 fs/ext4/inode.c:945
       ext4_quota_write+0x21e/0x570 fs/ext4/super.c:7165
       write_blk fs/quota/quota_tree.c:70 [inline]
       get_free_dqblk+0x355/0x6e0 fs/quota/quota_tree.c:136
       do_insert_tree+0x2b1/0x1460 fs/quota/quota_tree.c:347
       do_insert_tree+0xba9/0x1460 fs/quota/quota_tree.c:402
       do_insert_tree+0xba9/0x1460 fs/quota/quota_tree.c:402
       do_insert_tree+0xb68/0x1460 fs/quota/quota_tree.c:402
       dq_insert_tree fs/quota/quota_tree.c:432 [inline]
       qtree_write_dquot+0x483/0x5a0 fs/quota/quota_tree.c:451
       v2_write_dquot+0x11c/0x190 fs/quota/quota_v2.c:361
       dquot_acquire+0x34d/0x680 fs/quota/dquot.c:472
       ext4_acquire_dquot+0x2eb/0x4a0 fs/ext4/super.c:6791
       dqget+0x762/0xe90 fs/quota/dquot.c:988
       __dquot_initialize+0x2d9/0xea0 fs/quota/dquot.c:1517
       ext4_process_orphan+0x57/0x2d0 fs/ext4/orphan.c:329
       ext4_orphan_cleanup+0xb70/0x1400 fs/ext4/orphan.c:474
       __ext4_fill_super fs/ext4/super.c:5523 [inline]
       ext4_fill_super+0x84b2/0x89e0 fs/ext4/super.c:5654
       get_tree_bdev+0x3fe/0x620 fs/super.c:1366
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x2ba/0xb40 fs/namespace.c:3056
       do_mount fs/namespace.c:3399 [inline]
       __do_sys_mount fs/namespace.c:3607 [inline]
       __se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3584
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_read+0xad/0xa30 kernel/locking/rwsem.c:1520
       v2_read_dquot+0x4a/0x100 fs/quota/quota_v2.c:335
       dquot_acquire+0x188/0x680 fs/quota/dquot.c:463
       ext4_acquire_dquot+0x2eb/0x4a0 fs/ext4/super.c:6791
       dqget+0x762/0xe90 fs/quota/dquot.c:988
       __dquot_initialize+0x2d9/0xea0 fs/quota/dquot.c:1517
       ext4_symlink+0x1ea/0xc20 fs/ext4/namei.c:3431
       vfs_symlink+0x247/0x3d0 fs/namei.c:4471
       do_symlinkat+0x21e/0x390 fs/namei.c:4500
       __do_sys_symlink fs/namei.c:4522 [inline]
       __se_sys_symlink fs/namei.c:4520 [inline]
       __x64_sys_symlink+0x7a/0x90 fs/namei.c:4520
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&dquot->dq_lock){+.+.}-{3:3}:
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x132/0xd80 kernel/locking/mutex.c:747
       dquot_commit+0x57/0x510 fs/quota/dquot.c:507
       ext4_write_dquot+0x1fd/0x360 fs/ext4/super.c:6771
       mark_dquot_dirty fs/quota/dquot.c:372 [inline]
       mark_all_dquot_dirty+0xf7/0x400 fs/quota/dquot.c:412
       __dquot_alloc_space+0xb68/0x10e0 fs/quota/dquot.c:1752
       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:494 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
       ext4_ioctl+0x552e/0x5f80 fs/ext4/ioctl.c:1614
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&ei->i_data_sem/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
       down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
       swap_inode_boot_loader fs/ext4/ioctl.c:426 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
       ext4_ioctl+0x461f/0x5f80 fs/ext4/ioctl.c:1614
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:870 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
       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.4.1680/11518:
 #0: ffff888072b78460 (sb_writers#20){.+.+}-{0:0}, at: mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:437
 #1: ffff888055462c20 (&sb->s_type->i_mutex_key#25){++++}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff888055462c20 (&sb->s_type->i_mutex_key#25){++++}-{3:3}, at: lock_two_nondirectories+0xde/0x130 fs/inode.c:1208
 #2: ffff888055463628 (&sb->s_type->i_mutex_key#25/4){+.+.}-{3:3}, at: swap_inode_boot_loader fs/ext4/ioctl.c:385 [inline]
 #2: ffff888055463628 (&sb->s_type->i_mutex_key#25/4){+.+.}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
 #2: ffff888055463628 (&sb->s_type->i_mutex_key#25/4){+.+.}-{3:3}, at: ext4_ioctl+0x25fe/0x5f80 fs/ext4/ioctl.c:1614
 #3: ffff8880554637c8 (mapping.invalidate_lock#5){+.+.}-{3:3}, at: filemap_invalidate_lock include/linux/fs.h:803 [inline]
 #3: ffff8880554637c8 (mapping.invalidate_lock#5){+.+.}-{3:3}, at: swap_inode_boot_loader fs/ext4/ioctl.c:402 [inline]
 #3: ffff8880554637c8 (mapping.invalidate_lock#5){+.+.}-{3:3}, at: __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
 #3: ffff8880554637c8 (mapping.invalidate_lock#5){+.+.}-{3:3}, at: ext4_ioctl+0x42e7/0x5f80 fs/ext4/ioctl.c:1614
 #4: ffff888055462aa8 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40

stack backtrace:
CPU: 0 PID: 11518 Comm: syz.4.1680 Not tainted 6.1.129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
 down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
 swap_inode_boot_loader fs/ext4/ioctl.c:426 [inline]
 __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
 ext4_ioctl+0x461f/0x5f80 fs/ext4/ioctl.c:1614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe7b4d8d169
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:00007fe7b5c73038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe7b4fa6160 RCX: 00007fe7b4d8d169
RDX: 0000000000000000 RSI: 0000000000006611 RDI: 0000000000000008
RBP: 00007fe7b4e0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe7b4fa6160 R15: 00007ffd644f2f38
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/03 02:49 linux-6.1.y 3a8358583626 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in ext4_ioctl
2024/12/07 15:59 linux-6.1.y e4d90d63d385 9ac0fdc6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in ext4_ioctl
* Struck through repros no longer work on HEAD.