syzbot


possible deadlock in ext4_xattr_set_handle (4)

Status: upstream: reported on 2023/09/22 04:51
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+ea0ba556b26f54698271@syzkaller.appspotmail.com
First crash: 83d, last: 27d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [ext4?] possible deadlock in ext4_xattr_set_handle (4) 0 (1) 2023/09/22 04:51
Similar bugs (6)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ext4_xattr_set_handle (3) ext4 C 451 162d 319d 24/25 fixed on 2023/07/01 16:05
upstream possible deadlock in ext4_xattr_set_handle ext4 1 783d 779d 0/25 auto-closed as invalid on 2022/02/15 19:59
upstream possible deadlock in ext4_xattr_set_handle (2) ext4 1 517d 516d 0/25 auto-obsoleted due to no activity on 2022/11/08 16:24
linux-5.15 possible deadlock in ext4_xattr_set_handle C done 42 185d 278d 3/3 fixed on 2023/07/17 13:09
linux-4.19 possible deadlock in ext4_xattr_set_handle ext4 1 310d 310d 0/1 upstream: reported on 2023/02/03 16:43
linux-6.1 possible deadlock in ext4_xattr_set_handle C done 15 185d 273d 3/3 fixed on 2023/07/17 13:09

Sample crash report:
ext4 filesystem being mounted at /syzkaller-testdir3138044427/syzkaller.n0ylJN/804/file0 supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
6.6.0-syzkaller-16201-gb57b17e88bf5 #0 Not tainted
------------------------------------------------------
syz-executor.1/13825 is trying to acquire lock:
ffffffff8d11d1a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:303 [inline]
ffffffff8d11d1a0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slab.h:710 [inline]
ffffffff8d11d1a0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:3460 [inline]
ffffffff8d11d1a0 (fs_reclaim){+.+.}-{0:0}, at: __kmem_cache_alloc_node+0x51/0x310 mm/slub.c:3517

but task is already holding lock:
ffff888079acdac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
ffff888079acdac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_set_handle+0x159/0x1420 fs/ext4/xattr.c:2371

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ei->xattr_sem){++++}-{3:3}:
       down_write+0x93/0x200 kernel/locking/rwsem.c:1579
       ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
       ext4_xattr_set_handle+0x159/0x1420 fs/ext4/xattr.c:2371
       ext4_xattr_set+0x149/0x370 fs/ext4/xattr.c:2558
       __vfs_setxattr+0x173/0x1d0 fs/xattr.c:201
       __vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:235
       __vfs_setxattr_locked+0x17e/0x250 fs/xattr.c:296
       vfs_setxattr+0x146/0x350 fs/xattr.c:322
       do_setxattr+0x142/0x170 fs/xattr.c:630
       setxattr+0x159/0x170 fs/xattr.c:653
       path_setxattr+0x175/0x1d0 fs/xattr.c:672
       __do_sys_lsetxattr fs/xattr.c:695 [inline]
       __se_sys_lsetxattr fs/xattr.c:691 [inline]
       __ia32_sys_lsetxattr+0xbd/0x150 fs/xattr.c:691
       do_syscall_32_irqs_on arch/x86/entry/common.c:164 [inline]
       __do_fast_syscall_32+0x61/0xe0 arch/x86/entry/common.c:230
       do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:255
       entry_SYSENTER_compat_after_hwframe+0x70/0x7a

-> #2 (jbd2_handle){++++}-{0:0}:
       start_this_handle+0x10fc/0x15e0 fs/jbd2/transaction.c:463
       jbd2__journal_start+0x391/0x690 fs/jbd2/transaction.c:520
       __ext4_journal_start_sb+0x40f/0x5c0 fs/ext4/ext4_jbd2.c:112
       ext4_sample_last_mounted fs/ext4/file.c:835 [inline]
       ext4_file_open+0x632/0xc80 fs/ext4/file.c:864
       do_dentry_open+0x8d4/0x18d0 fs/open.c:948
       do_open fs/namei.c:3622 [inline]
       path_openat+0x1d4e/0x2c40 fs/namei.c:3779
       do_filp_open+0x1de/0x430 fs/namei.c:3809
       do_sys_openat2+0x176/0x1e0 fs/open.c:1440
       do_sys_open fs/open.c:1455 [inline]
       __do_sys_openat fs/open.c:1471 [inline]
       __se_sys_openat fs/open.c:1466 [inline]
       __x64_sys_openat+0x175/0x210 fs/open.c:1466
       do_syscall_x64 arch/x86/entry/common.c:51 [inline]
       do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
       entry_SYSCALL_64_after_hwframe+0x63/0x6b

-> #1 (sb_internal){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1635 [inline]
       sb_start_intwrite include/linux/fs.h:1757 [inline]
       ext4_evict_inode+0xe55/0x1a30 fs/ext4/inode.c:212
       evict+0x2ed/0x6b0 fs/inode.c:664
       iput_final fs/inode.c:1775 [inline]
       iput.part.0+0x55e/0x7a0 fs/inode.c:1801
       iput+0x5c/0x80 fs/inode.c:1791
       dentry_unlink_inode+0x292/0x430 fs/dcache.c:401
       __dentry_kill+0x3b8/0x640 fs/dcache.c:607
       shrink_dentry_list+0x22b/0x7d0 fs/dcache.c:1201
       prune_dcache_sb+0xeb/0x150 fs/dcache.c:1282
       super_cache_scan+0x327/0x540 fs/super.c:228
       do_shrink_slab+0x428/0x1120 mm/shrinker.c:435
       shrink_slab_memcg mm/shrinker.c:548 [inline]
       shrink_slab+0xa83/0x1310 mm/shrinker.c:626
       shrink_one+0x4f7/0x700 mm/vmscan.c:4724
       shrink_many mm/vmscan.c:4776 [inline]
       lru_gen_shrink_node mm/vmscan.c:4893 [inline]
       shrink_node+0x20cd/0x3790 mm/vmscan.c:5833
       kswapd_shrink_node mm/vmscan.c:6638 [inline]
       balance_pgdat+0xa32/0x1b80 mm/vmscan.c:6828
       kswapd+0x5be/0xbf0 mm/vmscan.c:7088
       kthread+0x33c/0x440 kernel/kthread.c:388
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

-> #0 (fs_reclaim){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
       lock_acquire kernel/locking/lockdep.c:5753 [inline]
       lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
       __fs_reclaim_acquire mm/page_alloc.c:3693 [inline]
       fs_reclaim_acquire+0x100/0x150 mm/page_alloc.c:3707
       might_alloc include/linux/sched/mm.h:303 [inline]
       slab_pre_alloc_hook mm/slab.h:710 [inline]
       slab_alloc_node mm/slub.c:3460 [inline]
       __kmem_cache_alloc_node+0x51/0x310 mm/slub.c:3517
       __do_kmalloc_node mm/slab_common.c:1006 [inline]
       __kmalloc_node+0x52/0x110 mm/slab_common.c:1014
       kmalloc_node include/linux/slab.h:620 [inline]
       kvmalloc_node+0x6f/0x1a0 mm/util.c:607
       kvmalloc include/linux/slab.h:738 [inline]
       ext4_xattr_inode_cache_find fs/ext4/xattr.c:1535 [inline]
       ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1577 [inline]
       ext4_xattr_set_entry+0x1c3d/0x3ce0 fs/ext4/xattr.c:1719
       ext4_xattr_block_set+0x678/0x3180 fs/ext4/xattr.c:1970
       ext4_xattr_set_handle+0xd6e/0x1420 fs/ext4/xattr.c:2456
       ext4_xattr_set+0x149/0x370 fs/ext4/xattr.c:2558
       __vfs_setxattr+0x173/0x1d0 fs/xattr.c:201
       __vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:235
       __vfs_setxattr_locked+0x17e/0x250 fs/xattr.c:296
       vfs_setxattr+0x146/0x350 fs/xattr.c:322
       do_setxattr+0x142/0x170 fs/xattr.c:630
       setxattr+0x159/0x170 fs/xattr.c:653
       __do_sys_fsetxattr fs/xattr.c:709 [inline]
       __se_sys_fsetxattr fs/xattr.c:698 [inline]
       __ia32_sys_fsetxattr+0x25e/0x310 fs/xattr.c:698
       do_syscall_32_irqs_on arch/x86/entry/common.c:164 [inline]
       __do_fast_syscall_32+0x61/0xe0 arch/x86/entry/common.c:230
       do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:255
       entry_SYSENTER_compat_after_hwframe+0x70/0x7a

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> jbd2_handle --> &ei->xattr_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->xattr_sem);
                               lock(jbd2_handle);
                               lock(&ei->xattr_sem);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz-executor.1/13825:
 #0: ffff888022928418 (sb_writers#4){.+.+}-{0:0}, at: __do_sys_fsetxattr fs/xattr.c:707 [inline]
 #0: ffff888022928418 (sb_writers#4){.+.+}-{0:0}, at: __se_sys_fsetxattr fs/xattr.c:698 [inline]
 #0: ffff888022928418 (sb_writers#4){.+.+}-{0:0}, at: __ia32_sys_fsetxattr+0x17a/0x310 fs/xattr.c:698
 #1: ffff888079acde00 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock include/linux/fs.h:802 [inline]
 #1: ffff888079acde00 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: vfs_setxattr+0x123/0x350 fs/xattr.c:321
 #2: ffff888079acdac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_write_lock_xattr fs/ext4/xattr.h:155 [inline]
 #2: ffff888079acdac8 (&ei->xattr_sem){++++}-{3:3}, at: ext4_xattr_set_handle+0x159/0x1420 fs/ext4/xattr.c:2371

stack backtrace:
CPU: 0 PID: 13825 Comm: syz-executor.1 Not tainted 6.6.0-syzkaller-16201-gb57b17e88bf5 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
 check_noncircular+0x311/0x3f0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
 lock_acquire kernel/locking/lockdep.c:5753 [inline]
 lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
 __fs_reclaim_acquire mm/page_alloc.c:3693 [inline]
 fs_reclaim_acquire+0x100/0x150 mm/page_alloc.c:3707
 might_alloc include/linux/sched/mm.h:303 [inline]
 slab_pre_alloc_hook mm/slab.h:710 [inline]
 slab_alloc_node mm/slub.c:3460 [inline]
 __kmem_cache_alloc_node+0x51/0x310 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node+0x52/0x110 mm/slab_common.c:1014
 kmalloc_node include/linux/slab.h:620 [inline]
 kvmalloc_node+0x6f/0x1a0 mm/util.c:607
 kvmalloc include/linux/slab.h:738 [inline]
 ext4_xattr_inode_cache_find fs/ext4/xattr.c:1535 [inline]
 ext4_xattr_inode_lookup_create fs/ext4/xattr.c:1577 [inline]
 ext4_xattr_set_entry+0x1c3d/0x3ce0 fs/ext4/xattr.c:1719
 ext4_xattr_block_set+0x678/0x3180 fs/ext4/xattr.c:1970
 ext4_xattr_set_handle+0xd6e/0x1420 fs/ext4/xattr.c:2456
 ext4_xattr_set+0x149/0x370 fs/ext4/xattr.c:2558
 __vfs_setxattr+0x173/0x1d0 fs/xattr.c:201
 __vfs_setxattr_noperm+0x127/0x5e0 fs/xattr.c:235
 __vfs_setxattr_locked+0x17e/0x250 fs/xattr.c:296
 vfs_setxattr+0x146/0x350 fs/xattr.c:322
 do_setxattr+0x142/0x170 fs/xattr.c:630
 setxattr+0x159/0x170 fs/xattr.c:653
 __do_sys_fsetxattr fs/xattr.c:709 [inline]
 __se_sys_fsetxattr fs/xattr.c:698 [inline]
 __ia32_sys_fsetxattr+0x25e/0x310 fs/xattr.c:698
 do_syscall_32_irqs_on arch/x86/entry/common.c:164 [inline]
 __do_fast_syscall_32+0x61/0xe0 arch/x86/entry/common.c:230
 do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:255
 entry_SYSENTER_compat_after_hwframe+0x70/0x7a
RIP: 0023:0xf7f9a579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f7f955ac EFLAGS: 00000292 ORIG_RAX: 00000000000000e4
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000020000000
RDX: 0000000020000080 RSI: 0000000000001008 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	10 06                	adc    %al,(%rsi)
   2:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
   6:	10 07                	adc    %al,(%rdi)
   8:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
   c:	10 08                	adc    %cl,(%rax)
   e:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
  1e:	00 51 52             	add    %dl,0x52(%rcx)
  21:	55                   	push   %rbp
  22:	89 e5                	mov    %esp,%ebp
  24:	0f 34                	sysenter
  26:	cd 80                	int    $0x80
* 28:	5d                   	pop    %rbp <-- trapping instruction
  29:	5a                   	pop    %rdx
  2a:	59                   	pop    %rcx
  2b:	c3                   	ret
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	90                   	nop
  2f:	90                   	nop
  30:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/11/12 21:57 upstream b57b17e88bf5 6d6dbf8a .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in ext4_xattr_set_handle
2023/09/18 04:42 upstream e789286468a9 0b6a67ac .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in ext4_xattr_set_handle
* Struck through repros no longer work on HEAD.