Message-ID: <67a8c19f.050a0220.110943.001b.GAE@google.com>
Date: Sun, 09 Feb 2025 06:54:23 -0800
From: syzbot <syzbot+4d7417d6eb8b36554c0d@...kaller.appspotmail.com>
To: konishi.ryusuke@...il.com, linux-kernel@...r.kernel.org, 
	linux-nilfs@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [nilfs?] possible deadlock in nilfs_bmap_clear (2)

Hello,

syzbot found the following issue on:

HEAD commit:    5c8c229261f1 Merge tag 'kthreads-fixes-2025-02-04' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=113e93df980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1909f2f0d8e641ce
dashboard link: https://syzkaller.appspot.com/bug?extid=4d7417d6eb8b36554c0d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-5c8c2292.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fc7bd0937147/vmlinux-5c8c2292.xz
kernel image: https://storage.googleapis.com/syzbot-assets/55fb37b08731/bzImage-5c8c2292.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4d7417d6eb8b36554c0d@...kaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc1-syzkaller-00028-g5c8c229261f1 #0 Not tainted
------------------------------------------------------
kswapd0/77 is trying to acquire lock:
ffff888011b773c0 (&bmap->b_sem){++++}-{4:4}, at: nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305

but task is already holding lock:
ffffffff8ea392e0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
ffffffff8ea392e0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (fs_reclaim){+.+.}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __fs_reclaim_acquire mm/page_alloc.c:3853 [inline]
       fs_reclaim_acquire+0x88/0x130 mm/page_alloc.c:3867
       might_alloc include/linux/sched/mm.h:318 [inline]
       slab_pre_alloc_hook mm/slub.c:4066 [inline]
       slab_alloc_node mm/slub.c:4144 [inline]
       kmem_cache_alloc_node_noprof+0x48/0x380 mm/slub.c:4216
       __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
       alloc_skb include/linux/skbuff.h:1331 [inline]
       alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289
       uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
       kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207
       bus_uevent_store+0x116/0x170 drivers/base/bus.c:832
       kernfs_fop_write_iter+0x3a0/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0xacf/0xd10 fs/read_write.c:679
       ksys_write+0x18f/0x2b0 fs/read_write.c:731
       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

-> #2 (uevent_sock_mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline]
       kobject_uevent_net_broadcast+0x280/0x580 lib/kobject_uevent.c:410
       kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
       loop_set_size drivers/block/loop.c:235 [inline]
       loop_set_status+0x687/0x9e0 drivers/block/loop.c:1292
       lo_ioctl+0xcd9/0x2600
       blkdev_ioctl+0x57d/0x6a0 block/ioctl.c:693
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       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

-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       bio_queue_enter block/blk.h:77 [inline]
       blk_mq_submit_bio+0x14e1/0x25a0 block/blk-mq.c:3091
       __submit_bio+0x2cf/0x6a0 block/blk-core.c:628
       __submit_bio_noacct_mq block/blk-core.c:715 [inline]
       submit_bio_noacct_nocheck+0x4d3/0xe30 block/blk-core.c:744
       nilfs_mdt_submit_block+0x5c5/0x880 fs/nilfs2/mdt.c:153
       nilfs_mdt_read_block+0xeb/0x430 fs/nilfs2/mdt.c:178
       nilfs_mdt_get_block+0x10a/0xa30 fs/nilfs2/mdt.c:254
       nilfs_palloc_get_block+0x181/0x2a0 fs/nilfs2/alloc.c:239
       nilfs_palloc_get_desc_block fs/nilfs2/alloc.c:296 [inline]
       nilfs_palloc_prepare_alloc_entry+0x3ee/0x1070 fs/nilfs2/alloc.c:607
       nilfs_dat_prepare_alloc fs/nilfs2/dat.c:78 [inline]
       nilfs_dat_prepare_update+0x6e/0x320 fs/nilfs2/dat.c:250
       nilfs_direct_propagate+0x1ec/0x3c0 fs/nilfs2/direct.c:279
       nilfs_bmap_propagate+0x75/0x120 fs/nilfs2/bmap.c:329
       nilfs_collect_file_data+0x4d/0xd0 fs/nilfs2/segment.c:589
       nilfs_segctor_apply_buffers+0x184/0x340 fs/nilfs2/segment.c:1010
       nilfs_segctor_scan_file+0x791/0xa50 fs/nilfs2/segment.c:1059
       nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1221 [inline]
       nilfs_segctor_collect fs/nilfs2/segment.c:1547 [inline]
       nilfs_segctor_do_construct+0x1c2b/0x6ea0 fs/nilfs2/segment.c:2122
       nilfs_segctor_construct+0x181/0x6b0 fs/nilfs2/segment.c:2478
       nilfs_segctor_thread_construct fs/nilfs2/segment.c:2586 [inline]
       nilfs_segctor_thread+0x69e/0xe80 fs/nilfs2/segment.c:2700
       kthread+0x7a9/0x920 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 (&bmap->b_sem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       down_write+0x99/0x220 kernel/locking/rwsem.c:1577
       nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305
       nilfs_clear_inode+0x147/0x2a0 fs/nilfs2/inode.c:836
       nilfs_evict_inode+0x105/0x500 fs/nilfs2/inode.c:856
       evict+0x4e8/0x9a0 fs/inode.c:796
       dispose_list fs/inode.c:845 [inline]
       prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
       super_cache_scan+0x38c/0x4b0 fs/super.c:223
       do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
       shrink_slab_memcg mm/shrinker.c:550 [inline]
       shrink_slab+0x878/0x14d0 mm/shrinker.c:628
       shrink_one+0x43b/0x850 mm/vmscan.c:4868
       shrink_many mm/vmscan.c:4929 [inline]
       lru_gen_shrink_node mm/vmscan.c:5007 [inline]
       shrink_node+0x37c5/0x3e50 mm/vmscan.c:5978
       kswapd_shrink_node mm/vmscan.c:6807 [inline]
       balance_pgdat mm/vmscan.c:6999 [inline]
       kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
       kthread+0x7a9/0x920 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

other info that might help us debug this:

Chain exists of:
  &bmap->b_sem --> uevent_sock_mutex --> fs_reclaim

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(fs_reclaim);
                               lock(uevent_sock_mutex);
                               lock(fs_reclaim);
  lock(&bmap->b_sem);

 *** DEADLOCK ***

2 locks held by kswapd0/77:
 #0: ffffffff8ea392e0 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:6886 [inline]
 #0: ffffffff8ea392e0 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xb9f/0x3b10 mm/vmscan.c:7264
 #1: ffff888043b8c0e0 (&type->s_umount_key#49){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline]
 #1: ffff888043b8c0e0 (&type->s_umount_key#49){.+.+}-{4:4}, at: super_cache_scan+0x94/0x4b0 fs/super.c:196

stack backtrace:
CPU: 0 UID: 0 PID: 77 Comm: kswapd0 Not tainted 6.14.0-rc1-syzkaller-00028-g5c8c229261f1 #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:2076
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 down_write+0x99/0x220 kernel/locking/rwsem.c:1577
 nilfs_bmap_clear+0x29/0xa0 fs/nilfs2/bmap.c:305
 nilfs_clear_inode+0x147/0x2a0 fs/nilfs2/inode.c:836
 nilfs_evict_inode+0x105/0x500 fs/nilfs2/inode.c:856
 evict+0x4e8/0x9a0 fs/inode.c:796
 dispose_list fs/inode.c:845 [inline]
 prune_icache_sb+0x239/0x2f0 fs/inode.c:1033
 super_cache_scan+0x38c/0x4b0 fs/super.c:223
 do_shrink_slab+0x72d/0x1160 mm/shrinker.c:437
 shrink_slab_memcg mm/shrinker.c:550 [inline]
 shrink_slab+0x878/0x14d0 mm/shrinker.c:628
 shrink_one+0x43b/0x850 mm/vmscan.c:4868
 shrink_many mm/vmscan.c:4929 [inline]
 lru_gen_shrink_node mm/vmscan.c:5007 [inline]
 shrink_node+0x37c5/0x3e50 mm/vmscan.c:5978
 kswapd_shrink_node mm/vmscan.c:6807 [inline]
 balance_pgdat mm/vmscan.c:6999 [inline]
 kswapd+0x20f3/0x3b10 mm/vmscan.c:7264
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


---
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