Re: [syzbot] [jffs2?] possible deadlock in jffs2_do_clear_inode (2)

[syzbot <syzbot+743079a09058321247d8@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    50d05c7c76c9 Merge tag 'landlock-7.3-rc3' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152c679e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=85bc5cc2fc7394d9
dashboard link: https://syzkaller.appspot.com/bug?extid=743079a09058321247d8
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10ec21f9580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16715ef9580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-50d05c7c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/303a0ade8f9e/vmlinux-50d05c7c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/70b8ca71442b/bzImage-50d05c7c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+743079a09058321247d8@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/113 is trying to acquire lock:
ffff888013732c60 (&f->sem){+.+.}-{4:4}, at: jffs2_do_clear_inode+0x5a/0x470 fs/jffs2/readinode.c:1419

but task is already holding lock:
ffffffff8efc9a20 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0xbce/0x1f00 mm/vmscan.c:7292

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __fs_reclaim_acquire mm/page_alloc.c:4375 [inline]
       fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4389
       might_alloc include/linux/sched/mm.h:316 [inline]
       slab_pre_alloc_hook mm/slub.c:4636 [inline]
       slab_alloc_node mm/slub.c:4974 [inline]
       kmem_cache_alloc_noprof+0x63/0x6a0 mm/slub.c:5010
       jffs2_do_read_inode+0x307/0x520 fs/jffs2/readinode.c:1372
       jffs2_iget+0x32b/0xe30 fs/jffs2/fs.c:277
       jffs2_do_fill_super+0x44b/0xa50 fs/jffs2/fs.c:578
       jffs2_fill_super+0x283/0x370 fs/jffs2/super.c:290
       mtd_get_sb+0x2f0/0x4c0 drivers/mtd/mtdsuper.c:57
       mtd_get_sb_by_nr drivers/mtd/mtdsuper.c:88 [inline]
       get_tree_mtd+0x6f9/0x8a0 drivers/mtd/mtdsuper.c:141
       vfs_get_tree+0x92/0x320 fs/super.c:1947
       fc_mount fs/namespace.c:1198 [inline]
       do_new_mount_fc fs/namespace.c:3772 [inline]
       do_new_mount fs/namespace.c:3848 [inline]
       path_mount+0x7d0/0x24c0 fs/namespace.c:4168
       do_mount fs/namespace.c:4181 [inline]
       __do_sys_mount fs/namespace.c:4397 [inline]
       __se_sys_mount fs/namespace.c:4374 [inline]
       __ia32_sys_mount+0x292/0x310 fs/namespace.c:4374
       do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
       __do_fast_syscall_32+0x13a/0x8b0 arch/x86/entry/syscall_32.c:291
       do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:316
       entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #0 (&f->sem){+.+.}-{4:4}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
       lock_acquire kernel/locking/lockdep.c:5942 [inline]
       lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
       jffs2_do_clear_inode+0x5a/0x470 fs/jffs2/readinode.c:1419
       evict+0x3c2/0xad0 fs/inode.c:822
       dispose_list+0x117/0x1e0 fs/inode.c:864
       prune_icache_sb+0xea/0x150 fs/inode.c:1011
       super_cache_scan+0x3ac/0x5c0 fs/super.c:240
       do_shrink_slab+0x416/0x1200 mm/shrinker.c:443
       shrink_slab_memcg mm/shrinker.c:560 [inline]
       shrink_slab+0xa82/0x12e0 mm/shrinker.c:638
       shrink_one+0x398/0x850 mm/vmscan.c:5119
       shrink_many mm/vmscan.c:5180 [inline]
       lru_gen_shrink_node mm/vmscan.c:5258 [inline]
       shrink_node+0x2b20/0x4320 mm/vmscan.c:6247
       kswapd_shrink_node mm/vmscan.c:7101 [inline]
       balance_pgdat+0xb20/0x1f00 mm/vmscan.c:7279
       kswapd+0x556/0xb50 mm/vmscan.c:7555
       kthread+0x373/0x450 kernel/kthread.c:436
       ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(&f->sem);
                               lock(fs_reclaim);
  lock(&f->sem);

 *** DEADLOCK ***

locks held by kswapd0/113: 2, last CPU#0:
 #0: ffffffff8efc9a20 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0xbce/0x1f00 mm/vmscan.c:7292
 #1: ffff88802553c0e8 (&type->s_umount_key#58){++++}-{4:4}, at: super_trylock_shared fs/super.c:688 [inline]
 #1: ffff88802553c0e8 (&type->s_umount_key#58){++++}-{4:4}, at: super_cache_scan+0x9b/0x5c0 fs/super.c:213

stack backtrace:
CPU: 0 UID: 0 PID: 113 Comm: kswapd0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
 jffs2_do_clear_inode+0x5a/0x470 fs/jffs2/readinode.c:1419
 evict+0x3c2/0xad0 fs/inode.c:822
 dispose_list+0x117/0x1e0 fs/inode.c:864
 prune_icache_sb+0xea/0x150 fs/inode.c:1011
 super_cache_scan+0x3ac/0x5c0 fs/super.c:240
 do_shrink_slab+0x416/0x1200 mm/shrinker.c:443
 shrink_slab_memcg mm/shrinker.c:560 [inline]
 shrink_slab+0xa82/0x12e0 mm/shrinker.c:638
 shrink_one+0x398/0x850 mm/vmscan.c:5119
 shrink_many mm/vmscan.c:5180 [inline]
 lru_gen_shrink_node mm/vmscan.c:5258 [inline]
 shrink_node+0x2b20/0x4320 mm/vmscan.c:6247
 kswapd_shrink_node mm/vmscan.c:7101 [inline]
 balance_pgdat+0xb20/0x1f00 mm/vmscan.c:7279
 kswapd+0x556/0xb50 mm/vmscan.c:7555
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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