syzbot


possible deadlock in ext4_move_extents

Status: auto-obsoleted due to no activity on 2023/11/11 09:48
Reported-by: syzbot+140c12a4219e871a0532@syzkaller.appspotmail.com
First crash: 383d, last: 294d
Similar bugs (4)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ext4_move_extents ext4 133 395d 565d 0/26 auto-obsoleted due to no activity on 2023/08/22 15:17
linux-6.1 possible deadlock in ext4_move_extents (2) 4 42d 161d 0/3 upstream: reported on 2023/12/14 10:09
linux-5.15 possible deadlock in ext4_move_extents 3 319d 395d 0/3 auto-obsoleted due to no activity on 2023/10/16 22:21
linux-5.15 possible deadlock in ext4_move_extents (2) 2 122d 191d 0/3 auto-obsoleted due to no activity on 2024/05/01 17:40

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.1.42-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/27443 is trying to acquire lock:
ffff8880702cf0e0 (&ei->i_data_sem/1){+.+.}-{3:3}, at: ext4_move_extents+0x379/0xe40 fs/ext4/move_extent.c:610

but task is already holding lock:
ffff8880701c9698 (&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:5669
       down_read+0x43/0x2e0 kernel/locking/rwsem.c:1520
       ext4_map_blocks+0x37a/0x1ca0 fs/ext4/inode.c:574
       ext4_getblk+0x1eb/0x7c0 fs/ext4/inode.c:854
       ext4_bread+0x2a/0x170 fs/ext4/inode.c:910
       ext4_quota_write+0x21e/0x570 fs/ext4/super.c:7135
       write_blk fs/quota/quota_tree.c:64 [inline]
       get_free_dqblk+0x340/0x6c0 fs/quota/quota_tree.c:130
       do_insert_tree+0x299/0x1ae0 fs/quota/quota_tree.c:340
       do_insert_tree+0x72a/0x1ae0 fs/quota/quota_tree.c:375
       do_insert_tree+0x72a/0x1ae0 fs/quota/quota_tree.c:375
       do_insert_tree+0x72a/0x1ae0 fs/quota/quota_tree.c:375
       dq_insert_tree fs/quota/quota_tree.c:401 [inline]
       qtree_write_dquot+0x3b9/0x530 fs/quota/quota_tree.c:420
       v2_write_dquot+0x11c/0x190 fs/quota/quota_v2.c:358
       dquot_acquire+0x34d/0x680 fs/quota/dquot.c:444
       ext4_acquire_dquot+0x2e6/0x400 fs/ext4/super.c:6769
       dqget+0x98b/0xdb0 fs/quota/dquot.c:914
       __dquot_initialize+0x2d9/0xe10 fs/quota/dquot.c:1492
       ext4_create+0xb1/0x550 fs/ext4/namei.c:2822
       lookup_open fs/namei.c:3413 [inline]
       open_last_lookups fs/namei.c:3481 [inline]
       path_openat+0x12f1/0x2e60 fs/namei.c:3711
       do_filp_open+0x230/0x480 fs/namei.c:3741
       do_sys_openat2+0x13b/0x500 fs/open.c:1318
       do_sys_open fs/open.c:1334 [inline]
       __do_sys_creat fs/open.c:1410 [inline]
       __se_sys_creat fs/open.c:1404 [inline]
       __x64_sys_creat+0x11f/0x160 fs/open.c:1404
       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+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       down_read+0x43/0x2e0 kernel/locking/rwsem.c:1520
       v2_read_dquot+0x4a/0x100 fs/quota/quota_v2.c:332
       dquot_acquire+0x188/0x680 fs/quota/dquot.c:435
       ext4_acquire_dquot+0x2e6/0x400 fs/ext4/super.c:6769
       dqget+0x98b/0xdb0 fs/quota/dquot.c:914
       __dquot_initialize+0x2d9/0xe10 fs/quota/dquot.c:1492
       ext4_mkdir+0x197/0xce0 fs/ext4/namei.c:3005
       vfs_mkdir+0x3b6/0x590 fs/namei.c:4036
       do_mkdirat+0x260/0x520 fs/namei.c:4061
       __do_sys_mkdirat fs/namei.c:4076 [inline]
       __se_sys_mkdirat fs/namei.c:4074 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4074
       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+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       __mutex_lock_common+0x1d4/0x2520 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+0x57/0x510 fs/quota/dquot.c:479
       ext4_write_dquot+0x1e8/0x2b0 fs/ext4/super.c:6753
       mark_dquot_dirty fs/quota/dquot.c:346 [inline]
       mark_all_dquot_dirty fs/quota/dquot.c:384 [inline]
       __dquot_alloc_space+0x53a/0xf30 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:494 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1424 [inline]
       ext4_ioctl+0x551e/0x5f60 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: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:3098 [inline]
       check_prevs_add kernel/locking/lockdep.c:3217 [inline]
       validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
       __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
       lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
       down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
       ext4_move_extents+0x379/0xe40 fs/ext4/move_extent.c:610
       __ext4_ioctl fs/ext4/ioctl.c:1358 [inline]
       ext4_ioctl+0x3a8d/0x5f60 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: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.0/27443:
 #0: ffff88814bc0a460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x5a/0x1f0 fs/namespace.c:437
 #1: ffff8880701c9810 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
 #1: ffff8880701c9810 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: lock_two_nondirectories+0xde/0x130 fs/inode.c:1163
 #2: ffff8880702cf258 (&sb->s_type->i_mutex_key#8/4){+.+.}-{3:3}, at: ext4_move_extents+0x35e/0xe40 fs/ext4/move_extent.c:603
 #3: ffff8880701c9698 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_double_down_write_data_sem+0x28/0x40

stack backtrace:
CPU: 1 PID: 27443 Comm: syz-executor.0 Not tainted 6.1.42-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
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:2178
 check_prev_add kernel/locking/lockdep.c:3098 [inline]
 check_prevs_add kernel/locking/lockdep.c:3217 [inline]
 validate_chain+0x1667/0x58e0 kernel/locking/lockdep.c:3832
 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5669
 down_write_nested+0x39/0x60 kernel/locking/rwsem.c:1689
 ext4_move_extents+0x379/0xe40 fs/ext4/move_extent.c:610
 __ext4_ioctl fs/ext4/ioctl.c:1358 [inline]
 ext4_ioctl+0x3a8d/0x5f60 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:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f2f75e7cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2f76b2a0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2f75f9bf80 RCX: 00007f2f75e7cae9
RDX: 0000000020000080 RSI: 00000000c028660f RDI: 0000000000000009
RBP: 00007f2f75ec847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f2f75f9bf80 R15: 00007ffda49eef38
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/08/03 09:48 linux-6.1.y d2a6dc4eaf6d 39a91c18 .config console log report info ci2-linux-6-1-kasan possible deadlock in ext4_move_extents
2023/05/06 08:26 linux-6.1.y ca48fc16c493 de870ca5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in ext4_move_extents
* Struck through repros no longer work on HEAD.