syzbot


possible deadlock in exfat_iterate (2)

Status: upstream: reported on 2024/06/27 12:58
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+df3558df41609451e4ac@syzkaller.appspotmail.com
First crash: 25d, last: 23d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [exfat?] possible deadlock in exfat_iterate (2) 1 (3) 2024/06/27 23:13
Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in exfat_iterate origin:upstream C done 81 343d 476d 3/3 fixed on 2023/10/06 12:26
upstream possible deadlock in exfat_iterate exfat C error unreliable 236 343d 653d 0/27 auto-obsoleted due to no activity on 2023/10/19 11:29
linux-6.1 possible deadlock in exfat_iterate 148 345d 484d 0/3 auto-obsoleted due to no activity on 2023/10/18 04:53

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc5-syzkaller-00018-g55027e689933 #0 Not tainted
------------------------------------------------------
syz-executor.2/6265 is trying to acquire lock:
ffffffff8dd3ab20 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:334 [inline]
ffffffff8dd3ab20 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:3891 [inline]
ffffffff8dd3ab20 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:3981 [inline]
ffffffff8dd3ab20 (fs_reclaim){+.+.}-{0:0}, at: __do_kmalloc_node mm/slub.c:4121 [inline]
ffffffff8dd3ab20 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_noprof+0xb5/0x420 mm/slub.c:4135

but task is already holding lock:
ffff88804af1a0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_iterate+0x33f/0xad0 fs/exfat/dir.c:256

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sbi->s_lock#2){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       exfat_evict_inode+0x25b/0x340 fs/exfat/inode.c:725
       evict+0x2ed/0x6c0 fs/inode.c:667
       iput_final fs/inode.c:1741 [inline]
       iput.part.0+0x5a8/0x7f0 fs/inode.c:1767
       iput+0x5c/0x80 fs/inode.c:1757
       dentry_unlink_inode+0x295/0x480 fs/dcache.c:400
       __dentry_kill+0x1d0/0x600 fs/dcache.c:603
       shrink_kill fs/dcache.c:1048 [inline]
       shrink_dentry_list+0x140/0x5d0 fs/dcache.c:1075
       prune_dcache_sb+0xeb/0x150 fs/dcache.c:1156
       super_cache_scan+0x32a/0x550 fs/super.c:221
       do_shrink_slab+0x44f/0x11c0 mm/shrinker.c:435
       shrink_slab_memcg mm/shrinker.c:548 [inline]
       shrink_slab+0xa87/0x1310 mm/shrinker.c:626
       shrink_one+0x493/0x7c0 mm/vmscan.c:4790
       shrink_many mm/vmscan.c:4851 [inline]
       lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4951
       shrink_node mm/vmscan.c:5910 [inline]
       kswapd_shrink_node mm/vmscan.c:6720 [inline]
       balance_pgdat+0x1105/0x1970 mm/vmscan.c:6911
       kswapd+0x5ea/0xbf0 mm/vmscan.c:7180
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #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:3869 [inline]
       __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
       lock_acquire kernel/locking/lockdep.c:5754 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
       __fs_reclaim_acquire mm/page_alloc.c:3801 [inline]
       fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3815
       might_alloc include/linux/sched/mm.h:334 [inline]
       slab_pre_alloc_hook mm/slub.c:3891 [inline]
       slab_alloc_node mm/slub.c:3981 [inline]
       __do_kmalloc_node mm/slub.c:4121 [inline]
       __kmalloc_noprof+0xb5/0x420 mm/slub.c:4135
       kmalloc_noprof include/linux/slab.h:664 [inline]
       kmalloc_array_noprof include/linux/slab.h:699 [inline]
       __exfat_get_dentry_set+0x81e/0xa90 fs/exfat/dir.c:816
       exfat_get_dentry_set+0x36/0x210 fs/exfat/dir.c:859
       exfat_get_uniname_from_ext_entry fs/exfat/dir.c:39 [inline]
       exfat_readdir+0x950/0x1520 fs/exfat/dir.c:155
       exfat_iterate+0x3c7/0xad0 fs/exfat/dir.c:261
       wrap_directory_iterator+0xa5/0xe0 fs/readdir.c:67
       iterate_dir+0x53e/0xb60 fs/readdir.c:110
       __do_sys_getdents64 fs/readdir.c:409 [inline]
       __se_sys_getdents64 fs/readdir.c:394 [inline]
       __ia32_sys_getdents64+0x14f/0x2e0 fs/readdir.c:394
       do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
       __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
       do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
       entry_SYSENTER_compat_after_hwframe+0x84/0x8e

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->s_lock#2);
                               lock(fs_reclaim);
                               lock(&sbi->s_lock#2);
  lock(fs_reclaim);

 *** DEADLOCK ***

3 locks held by syz-executor.2/6265:
 #0: ffff88801db114c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xeb/0x180 fs/file.c:1191
 #1: ffff8880483da9e8 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: wrap_directory_iterator+0x5a/0xe0 fs/readdir.c:56
 #2: ffff88804af1a0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_iterate+0x33f/0xad0 fs/exfat/dir.c:256

stack backtrace:
CPU: 0 PID: 6265 Comm: syz-executor.2 Not tainted 6.10.0-rc5-syzkaller-00018-g55027e689933 #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+0x116/0x1f0 lib/dump_stack.c:114
 check_noncircular+0x31a/0x400 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:3869 [inline]
 __lock_acquire+0x2478/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 __fs_reclaim_acquire mm/page_alloc.c:3801 [inline]
 fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3815
 might_alloc include/linux/sched/mm.h:334 [inline]
 slab_pre_alloc_hook mm/slub.c:3891 [inline]
 slab_alloc_node mm/slub.c:3981 [inline]
 __do_kmalloc_node mm/slub.c:4121 [inline]
 __kmalloc_noprof+0xb5/0x420 mm/slub.c:4135
 kmalloc_noprof include/linux/slab.h:664 [inline]
 kmalloc_array_noprof include/linux/slab.h:699 [inline]
 __exfat_get_dentry_set+0x81e/0xa90 fs/exfat/dir.c:816
 exfat_get_dentry_set+0x36/0x210 fs/exfat/dir.c:859
 exfat_get_uniname_from_ext_entry fs/exfat/dir.c:39 [inline]
 exfat_readdir+0x950/0x1520 fs/exfat/dir.c:155
 exfat_iterate+0x3c7/0xad0 fs/exfat/dir.c:261
 wrap_directory_iterator+0xa5/0xe0 fs/readdir.c:67
 iterate_dir+0x53e/0xb60 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:409 [inline]
 __se_sys_getdents64 fs/readdir.c:394 [inline]
 __ia32_sys_getdents64+0x14f/0x2e0 fs/readdir.c:394
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf72f8579
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:00000000f5ec95ac EFLAGS: 00000292 ORIG_RAX: 00000000000000dc
RAX: ffffffffffffffda RBX: 000000000000000a RCX: 0000000020002ec0
RDX: 0000000000001000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 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
2024/06/25 22:18 upstream 55027e689933 c2e07261 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in exfat_iterate
2024/06/23 12:55 upstream 5f583a3162ff c2e07261 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in exfat_iterate
* Struck through repros no longer work on HEAD.