syzbot


possible deadlock in ext4_xattr_set_entry

Status: upstream: reported C repro on 2025/02/15 09:05
Reported-by: syzbot+aee2d0876b688d945095@syzkaller.appspotmail.com
First crash: 24d, last: 10d
Bug presence (1)
Date Name Commit Repro Result
2025/03/02 upstream (ToT) ece144f151ac C Failed due to an error; will retry later
Last patch testing requests (2)
Created Duration User Patch Repo Result
2025/03/01 19:53 10m retest repro linux-5.15.y report log
2025/03/01 19:53 1h05m retest repro linux-5.15.y report log

Sample crash report:
EXT4-fs (loop3): mounted filesystem without journal. Opts: nojournal_checksum,nombcache,barrier,norecovery,debug_want_extra_isize=0x0000000000000080,lazytime,nodelalloc,usrquota,noauto_da_alloc,bh,init_itable,,errors=continue. Quota mode: writeback.
======================================================
WARNING: possible circular locking dependency detected
5.15.178-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor104/4437 is trying to acquire lock:
ffff888066ccc9b8 (&sb->s_type->i_mutex_key#9/1){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
ffff888066ccc9b8 (&sb->s_type->i_mutex_key#9/1){+.+.}-{3:3}, at: ext4_xattr_inode_create fs/ext4/xattr.c:1465 [inline]
ffff888066ccc9b8 (&sb->s_type->i_mutex_key#9/1){+.+.}-{3:3}, at: ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1547 [inline]
ffff888066ccc9b8 (&sb->s_type->i_mutex_key#9/1){+.+.}-{3:3}, at: ext4_xattr_set_entry+0x3713/0x4130 fs/ext4/xattr.c:1675

but task is already holding lock:
ffff888066cb8278 (&ei->i_data_sem/3){++++}-{3:3}, at: ext4_truncate+0x974/0x1130 fs/ext4/inode.c:4244

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ei->i_data_sem/3){++++}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       ext4_update_i_disksize fs/ext4/ext4.h:3401 [inline]
       ext4_xattr_inode_write fs/ext4/xattr.c:1403 [inline]
       ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1551 [inline]
       ext4_xattr_set_entry+0x35e2/0x4130 fs/ext4/xattr.c:1675
       ext4_xattr_ibody_set+0x11d/0x330 fs/ext4/xattr.c:2243
       ext4_xattr_set_handle+0xc72/0x1560 fs/ext4/xattr.c:2400
       ext4_xattr_set+0x26e/0x3d0 fs/ext4/xattr.c:2513
       __vfs_setxattr+0x3e7/0x420 fs/xattr.c:182
       __vfs_setxattr_noperm+0x12a/0x5e0 fs/xattr.c:216
       vfs_setxattr+0x21d/0x420 fs/xattr.c:303
       do_setxattr fs/xattr.c:588 [inline]
       setxattr+0x27e/0x2e0 fs/xattr.c:611
       path_setxattr+0x1bc/0x2a0 fs/xattr.c:630
       __do_sys_setxattr fs/xattr.c:646 [inline]
       __se_sys_setxattr fs/xattr.c:642 [inline]
       __x64_sys_setxattr+0xb7/0xd0 fs/xattr.c:642
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&sb->s_type->i_mutex_key#9/1){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       inode_lock include/linux/fs.h:789 [inline]
       ext4_xattr_inode_create fs/ext4/xattr.c:1465 [inline]
       ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1547 [inline]
       ext4_xattr_set_entry+0x3713/0x4130 fs/ext4/xattr.c:1675
       ext4_xattr_block_set+0xb10/0x36a0 fs/ext4/xattr.c:1995
       ext4_xattr_move_to_block fs/ext4/xattr.c:2623 [inline]
       ext4_xattr_make_inode_space fs/ext4/xattr.c:2698 [inline]
       ext4_expand_extra_isize_ea+0x10d5/0x1bb0 fs/ext4/xattr.c:2790
       __ext4_expand_extra_isize+0x2f7/0x3d0 fs/ext4/inode.c:5857
       ext4_try_to_expand_extra_isize fs/ext4/inode.c:5900 [inline]
       __ext4_mark_inode_dirty+0x539/0x860 fs/ext4/inode.c:5978
       ext4_ext_truncate+0x9a/0x250 fs/ext4/extents.c:4454
       ext4_truncate+0x9fd/0x1130 fs/ext4/inode.c:4249
       ext4_evict_inode+0xba1/0x1100 fs/ext4/inode.c:289
       evict+0x529/0x930 fs/inode.c:622
       __dentry_kill+0x436/0x650 fs/dcache.c:586
       dentry_kill+0xbb/0x290
       dput+0xd8/0x1a0 fs/dcache.c:893
       do_renameat2+0xe1c/0x1700 fs/namei.c:4987
       __do_sys_rename fs/namei.c:5031 [inline]
       __se_sys_rename fs/namei.c:5029 [inline]
       __x64_sys_rename+0x82/0x90 fs/namei.c:5029
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->i_data_sem/3);
                               lock(&sb->s_type->i_mutex_key#9/1);
                               lock(&ei->i_data_sem/3);
  lock(&sb->s_type->i_mutex_key#9/1);

 *** DEADLOCK ***

7 locks held by syz-executor104/4437:
 #0: ffff8880796da460 (sb_writers#5){.+.+}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377
 #1: ffff8880796da748 (&type->s_vfs_rename_key){+.+.}-{3:3}, at: lock_rename fs/namei.c:3016 [inline]
 #1: ffff8880796da748 (&type->s_vfs_rename_key){+.+.}-{3:3}, at: do_renameat2+0x5b7/0x1700 fs/namei.c:4924
 #2: ffff888066cbf198 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: lock_rename fs/namei.c:3017 [inline]
 #2: ffff888066cbf198 (&type->i_mutex_dir_key#4/1){+.+.}-{3:3}, at: do_renameat2+0x644/0x1700 fs/namei.c:4924
 #3: ffff888066cbe7a0 (&type->i_mutex_dir_key#4/5){+.+.}-{3:3}, at: do_renameat2+0x67e/0x1700 fs/namei.c:4924
 #4: ffff8880796da650 (sb_internal){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1813 [inline]
 #4: ffff8880796da650 (sb_internal){.+.+}-{0:0}, at: sb_start_intwrite include/linux/fs.h:1930 [inline]
 #4: ffff8880796da650 (sb_internal){.+.+}-{0:0}, at: ext4_evict_inode+0x375/0x1100 fs/ext4/inode.c:243
 #5: ffff888066cb8278 (&ei->i_data_sem/3){++++}-{3:3}, at: ext4_truncate+0x974/0x1130 fs/ext4/inode.c:4244
 #6: ffff888066cb80c8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_trylock_xattr fs/ext4/xattr.h:162 [inline]
 #6: ffff888066cb80c8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_try_to_expand_extra_isize fs/ext4/inode.c:5897 [inline]
 #6: ffff888066cb80c8 (&ei->xattr_sem){++++}-{3:3}, at: __ext4_mark_inode_dirty+0x4a0/0x860 fs/ext4/inode.c:5978

stack backtrace:
CPU: 0 PID: 4437 Comm: syz-executor104 Not tainted 5.15.178-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 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+0x1649/0x5930 kernel/locking/lockdep.c:3788
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
 down_write+0x38/0x60 kernel/locking/rwsem.c:1551
 inode_lock include/linux/fs.h:789 [inline]
 ext4_xattr_inode_create fs/ext4/xattr.c:1465 [inline]
 ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1547 [inline]
 ext4_xattr_set_entry+0x3713/0x4130 fs/ext4/xattr.c:1675
 ext4_xattr_block_set+0xb10/0x36a0 fs/ext4/xattr.c:1995
 ext4_xattr_move_to_block fs/ext4/xattr.c:2623 [inline]
 ext4_xattr_make_inode_space fs/ext4/xattr.c:2698 [inline]
 ext4_expand_extra_isize_ea+0x10d5/0x1bb0 fs/ext4/xattr.c:2790
 __ext4_expand_extra_isize+0x2f7/0x3d0 fs/ext4/inode.c:5857
 ext4_try_to_expand_extra_isize fs/ext4/inode.c:5900 [inline]
 __ext4_mark_inode_dirty+0x539/0x860 fs/ext4/inode.c:5978
 ext4_ext_truncate+0x9a/0x250 fs/ext4/extents.c:4454
 ext4_truncate+0x9fd/0x1130 fs/ext4/inode.c:4249
 ext4_evict_inode+0xba1/0x1100 fs/ext4/inode.c:289
 evict+0x529/0x930 fs/inode.c:622
 __dentry_kill+0x436/0x650 fs/dcache.c:586
 dentry_kill+0xbb/0x290
 dput+0xd8/0x1a0 fs/dcache.c:893
 do_renameat2+0xe1c/0x1700 fs/namei.c:4987
 __do_sys_rename fs/namei.c:5031 [inline]
 __se_sys_rename fs/namei.c:5029 [inline]
 __x64_sys_rename+0x82/0x90 fs/namei.c:5029
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd780a7abe9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 1f 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:00007fd780226168 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 0030656c69662f30 RCX: 00007fd780a7abe9
RDX: 2f30656c69662f2e RSI: 00004000000000c0 RDI: 0000400000000000
RBP: 00007fd780b02480 R08: 00007fd7802266c0 R09: 00007fd780b02488
R10: 00007fd780b02488 R11: 0000000000000246 R12: 00007fd780b0248c
R13: 000000000000000b R14: 00007ffcea1c8660 R15: 00007ffcea1c8748
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/15 16:38 linux-5.15.y c16c81c81336 40a34ec9 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan possible deadlock in ext4_xattr_set_entry
2025/02/15 15:14 linux-5.15.y c16c81c81336 40a34ec9 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-linux-5-15-kasan possible deadlock in ext4_xattr_set_entry
2025/02/15 09:05 linux-5.15.y c16c81c81336 40a34ec9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_xattr_set_entry
* Struck through repros no longer work on HEAD.