syzbot


possible deadlock in exfat_evict_inode

Status: upstream: reported on 2024/05/18 20:20
Subsystems: exfat
[Documentation on labels]
Reported-by: syzbot+412a392a2cd4a65e71db@syzkaller.appspotmail.com
Fix commit: exfat: fix potential deadlock on __exfat_get_dentry_set
Patched on: [ci-upstream-linux-next-kasan-gce-root], missing on: [ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-net-next-test-gce ci2-upstream-usb]
First crash: 38d, last: 38d
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] exfat: fix potential deadlock on __exfat_get_dentry_set 2 (2) 2024/06/03 11:50
[syzbot] [exfat?] possible deadlock in exfat_evict_inode 0 (1) 2024/05/18 20:20

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-01893-g6bfd2d442af5 #0 Not tainted
------------------------------------------------------
kswapd0/112 is trying to acquire lock:
ffff88801d68c0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_evict_inode+0x25b/0x340 fs/exfat/inode.c:725

but task is already holding lock:
ffffffff8d9390c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       __fs_reclaim_acquire mm/page_alloc.c:3698 [inline]
       fs_reclaim_acquire+0x102/0x160 mm/page_alloc.c:3712
       might_alloc include/linux/sched/mm.h:312 [inline]
       slab_pre_alloc_hook mm/slub.c:3819 [inline]
       slab_alloc_node mm/slub.c:3900 [inline]
       __do_kmalloc_node mm/slub.c:4038 [inline]
       __kmalloc+0xb5/0x440 mm/slub.c:4052
       kmalloc_array include/linux/slab.h:665 [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+0x292/0x9e0 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+0x75/0x120 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

-> #0 (&sbi->s_lock#2){+.+.}-{3:3}:
       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
       __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+0x295/0x440 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:4774
       shrink_many mm/vmscan.c:4835 [inline]
       lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
       shrink_node mm/vmscan.c:5894 [inline]
       kswapd_shrink_node mm/vmscan.c:6704 [inline]
       balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
       kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
       kthread+0x2c1/0x3a0 kernel/kthread.c:388
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

2 locks held by kswapd0/112:
 #0: ffffffff8d9390c0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x166/0x1a10 mm/vmscan.c:6782
 #1: ffff88801d6880e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_trylock_shared fs/super.c:561 [inline]
 #1: ffff88801d6880e0 (&type->s_umount_key#87){++++}-{3:3}, at: super_cache_scan+0x96/0x550 fs/super.c:196

stack backtrace:
CPU: 2 PID: 112 Comm: kswapd0 Not tainted 6.9.0-syzkaller-01893-g6bfd2d442af5 #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
 __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+0x295/0x440 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:4774
 shrink_many mm/vmscan.c:4835 [inline]
 lru_gen_shrink_node+0x89f/0x1750 mm/vmscan.c:4935
 shrink_node mm/vmscan.c:5894 [inline]
 kswapd_shrink_node mm/vmscan.c:6704 [inline]
 balance_pgdat+0x10d1/0x1a10 mm/vmscan.c:6895
 kswapd+0x5ea/0xbf0 mm/vmscan.c:7164
 kthread+0x2c1/0x3a0 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/14 20:12 upstream 6bfd2d442af5 fdb4c10c .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 possible deadlock in exfat_evict_inode
* Struck through repros no longer work on HEAD.