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Message-ID: <66f65bf1.050a0220.46d20.0010.GAE@google.com>
Date: Fri, 27 Sep 2024 00:17:05 -0700
From: syzbot <syzbot+c679f13773f295d2da53@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, lizhi.xu@...driver.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [squashfs?] possible deadlock in fsnotify_destroy_mark

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in fsnotify_destroy_mark

======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-11558-g075dbe9f6e3c-dirty #0 Not tainted
------------------------------------------------------
kswapd0/80 is trying to acquire lock:
ffff888051323930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline]
ffff888051323930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578

but task is already holding lock:
ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbb4/0x3590 mm/vmscan.c:7226

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
       __fs_reclaim_acquire mm/page_alloc.c:3834 [inline]
       fs_reclaim_acquire+0x88/0x140 mm/page_alloc.c:3848
       might_alloc include/linux/sched/mm.h:327 [inline]
       slab_pre_alloc_hook mm/slub.c:4037 [inline]
       slab_alloc_node mm/slub.c:4115 [inline]
       __kmalloc_cache_noprof+0x3d/0x2c0 mm/slub.c:4291
       kmalloc_noprof include/linux/slab.h:878 [inline]
       kzalloc_noprof include/linux/slab.h:1014 [inline]
       fsnotify_attach_info_to_sb fs/notify/mark.c:626 [inline]
       fsnotify_add_mark_list fs/notify/mark.c:718 [inline]
       fsnotify_add_mark_locked+0x3b2/0xdc0 fs/notify/mark.c:803
       fsnotify_add_inode_mark_locked include/linux/fsnotify_backend.h:814 [inline]
       inotify_new_watch fs/notify/inotify/inotify_user.c:620 [inline]
       inotify_update_watch fs/notify/inotify/inotify_user.c:647 [inline]
       __do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:786 [inline]
       __se_sys_inotify_add_watch+0xa83/0x1060 fs/notify/inotify/inotify_user.c:729
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&group->mark_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3158 [inline]
       check_prevs_add kernel/locking/lockdep.c:3277 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline]
       fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578
       fsnotify_destroy_marks+0x14a/0x660 fs/notify/mark.c:934
       fsnotify_inoderemove include/linux/fsnotify.h:264 [inline]
       dentry_unlink_inode+0x2e0/0x430 fs/dcache.c:408
       __dentry_kill+0x20d/0x630 fs/dcache.c:615
       shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
       shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
       prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
       super_cache_scan+0x34f/0x4b0 fs/super.c:221
       do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
       shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
       shrink_one+0x43b/0x850 mm/vmscan.c:4818
       shrink_many mm/vmscan.c:4879 [inline]
       lru_gen_shrink_node mm/vmscan.c:4957 [inline]
       shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
       kswapd_shrink_node mm/vmscan.c:6765 [inline]
       balance_pgdat mm/vmscan.c:6957 [inline]
       kswapd+0x1bb4/0x3590 mm/vmscan.c:7226
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/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(&group->mark_mutex);
                               lock(fs_reclaim);
  lock(&group->mark_mutex);

 *** DEADLOCK ***

2 locks held by kswapd0/80:
 #0: ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6844 [inline]
 #0: ffffffff8ea37100 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbb4/0x3590 mm/vmscan.c:7226
 #1: ffff8880003380e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff8880003380e0 (&type->s_umount_key#54){.+.+}-{3:3}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 80 Comm: kswapd0 Not tainted 6.11.0-syzkaller-11558-g075dbe9f6e3c-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2203
 check_prev_add kernel/locking/lockdep.c:3158 [inline]
 check_prevs_add kernel/locking/lockdep.c:3277 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline]
 fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578
 fsnotify_destroy_marks+0x14a/0x660 fs/notify/mark.c:934
 fsnotify_inoderemove include/linux/fsnotify.h:264 [inline]
 dentry_unlink_inode+0x2e0/0x430 fs/dcache.c:408
 __dentry_kill+0x20d/0x630 fs/dcache.c:615
 shrink_kill+0xa9/0x2c0 fs/dcache.c:1060
 shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1087
 prune_dcache_sb+0x10f/0x180 fs/dcache.c:1168
 super_cache_scan+0x34f/0x4b0 fs/super.c:221
 do_shrink_slab+0x701/0x1160 mm/shrinker.c:435
 shrink_slab+0x1093/0x14d0 mm/shrinker.c:662
 shrink_one+0x43b/0x850 mm/vmscan.c:4818
 shrink_many mm/vmscan.c:4879 [inline]
 lru_gen_shrink_node mm/vmscan.c:4957 [inline]
 shrink_node+0x3799/0x3de0 mm/vmscan.c:5937
 kswapd_shrink_node mm/vmscan.c:6765 [inline]
 balance_pgdat mm/vmscan.c:6957 [inline]
 kswapd+0x1bb4/0x3590 mm/vmscan.c:7226
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


Tested on:

commit:         075dbe9f Merge tag 'soc-ep93xx-dt-6.12' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13eaba80580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5f49dd07427b3bf8
dashboard link: https://syzkaller.appspot.com/bug?extid=c679f13773f295d2da53
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1736bb3b980000

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