bisecting fixing commit since e7c124bd04631973a3cc0df19ab881b56d8a2d50 building syzkaller on 6cc879d4712dbaf6e97f01250e2f4906c07b24b8 testing commit e7c124bd04631973a3cc0df19ab881b56d8a2d50 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: b276f2a3e0c7d820aa61aec159c3e095c93dbc91d99d42e22fa0d4ffc23d7626 run #0: crashed: WARNING in kernfs_remove_by_name_ns run #1: crashed: WARNING in kernfs_remove_by_name_ns run #2: crashed: WARNING in kernfs_remove_by_name_ns run #3: crashed: WARNING in kernfs_remove_by_name_ns run #4: crashed: WARNING in kernfs_remove_by_name_ns run #5: crashed: WARNING in kernfs_remove_by_name_ns run #6: crashed: WARNING in kernfs_remove_by_name_ns run #7: crashed: WARNING in kernfs_remove_by_name_ns run #8: crashed: WARNING in kernfs_remove_by_name_ns run #9: crashed: WARNING in kernfs_remove_by_name_ns run #10: crashed: WARNING in kernfs_remove_by_name_ns run #11: crashed: WARNING in kernfs_remove_by_name_ns run #12: crashed: WARNING in kernfs_remove_by_name_ns run #13: crashed: WARNING in kernfs_remove_by_name_ns run #14: crashed: WARNING in kernfs_remove_by_name_ns run #15: crashed: WARNING in kernfs_remove_by_name_ns run #16: crashed: WARNING in kernfs_remove_by_name_ns run #17: OK run #18: OK run #19: OK testing current HEAD e8b767f5e04097aaedcd6e06e2270f9fe5282696 testing commit e8b767f5e04097aaedcd6e06e2270f9fe5282696 compiler: gcc (GCC) 10.2.1 20210217, GNU ld (GNU Binutils for Debian) 2.35.2 kernel signature: 409d5c90db790d1155b11d380e19627cb1c5540d02d8c14508f8b20a3d59d9cb all runs: crashed: WARNING in kernfs_remove_by_name_ns revisions tested: 2, total time: 21m45.122292447s (build: 12m26.330854809s, test: 8m44.484313466s) the crash still happens on HEAD commit msg: Merge tag 'for-linus-5.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml crash: WARNING in kernfs_remove_by_name_ns kernfs: can not remove 'nr_tags', no directory WARNING: CPU: 1 PID: 4482 at fs/kernfs/dir.c:1564 kernfs_remove_by_name_ns+0xbb/0xe0 fs/kernfs/dir.c:1564 Modules linked in: CPU: 1 PID: 4482 Comm: syz-executor403 Tainted: G W 5.17.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:kernfs_remove_by_name_ns+0xbb/0xe0 fs/kernfs/dir.c:1564 Code: 5b 2c 75 ff 31 c0 5b 5d 41 5c 41 5d 41 5e c3 4c 89 e7 e8 48 2c 75 ff b8 fe ff ff ff eb e8 48 c7 c7 a0 ac fc 88 e8 a9 a0 6c 06 <0f> 0b b8 fe ff ff ff eb d3 e8 27 eb ce ff eb 94 e8 20 eb ce ff e9 RSP: 0018:ffffc9000566fa60 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffffffff8b5e9f48 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000008 RDI: fffff52000acdf3e RBP: ffffffff8b5ea040 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 7374656b636f7362 R12: 0000000000000000 R13: dffffc0000000000 R14: ffffffff893f6e60 R15: ffff88801b37f800 FS: 00007f2b25adb700(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2b25b1cec8 CR3: 0000000078306000 CR4: 00000000003506e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: kernfs_remove_by_name include/linux/kernfs.h:558 [inline] remove_files+0x87/0x1a0 fs/sysfs/group.c:28 sysfs_remove_group+0x72/0x140 fs/sysfs/group.c:288 sysfs_remove_groups fs/sysfs/group.c:312 [inline] sysfs_remove_groups+0x4a/0x90 fs/sysfs/group.c:304 __kobject_del+0x7d/0x1b0 lib/kobject.c:611 kobject_del lib/kobject.c:643 [inline] kobject_del+0x32/0x50 lib/kobject.c:635 blk_mq_unregister_hctx block/blk-mq-sysfs.c:181 [inline] blk_mq_unregister_hctx block/blk-mq-sysfs.c:170 [inline] blk_mq_sysfs_unregister+0x1f6/0x270 block/blk-mq-sysfs.c:303 __blk_mq_update_nr_hw_queues block/blk-mq.c:4517 [inline] blk_mq_update_nr_hw_queues+0x416/0xda0 block/blk-mq.c:4563 nbd_start_device+0x10a/0xb70 drivers/block/nbd.c:1347 nbd_start_device_ioctl drivers/block/nbd.c:1397 [inline] __nbd_ioctl drivers/block/nbd.c:1471 [inline] nbd_ioctl+0x3ba/0x8f0 drivers/block/nbd.c:1511 blkdev_ioctl+0x2ff/0x660 block/ioctl.c:588 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x11f/0x190 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f2b25b70369 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f2b25adb2e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f2b25bf4500 RCX: 00007f2b25b70369 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000006 RBP: 00007f2b25bc1184 R08: 0000000000000001 R09: 0000000000000035 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f2b25bf450c R13: 00007f2b25adb2f0 R14: 00007f2b25bf4508 R15: 0000000000000001