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@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== 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> --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup
