In the Linux kernel, the following vulnerability has been resolved:[EOL][EOL]blk-mq: check kobject state_in_sysfs before deleting in blk_mq_unregister_hctx[EOL][EOL]In __blk_mq_update_nr_hw_queues() the return value of[EOL]blk_mq_sysfs_register_hctxs() is not checked. If sysfs creation for hctx[EOL]fails, later changing the number of hw_queues or removing disk will[EOL]trigger the following warning:[EOL][EOL] kernfs: can not remove 'nr_tags', no directory[EOL] WARNING: CPU: 2 PID: 637 at fs/kernfs/dir.c:1707 kernfs_remove_by_name_ns+0x13f/0x160[EOL] Call Trace:[EOL] remove_files.isra.1+0x38/0xb0[EOL] sysfs_remove_group+0x4d/0x100[EOL] sysfs_remove_groups+0x31/0x60[EOL] __kobject_del+0x23/0xf0[EOL] kobject_del+0x17/0x40[EOL] blk_mq_unregister_hctx+0x5d/0x80[EOL] blk_mq_sysfs_unregister_hctxs+0x94/0xd0[EOL] blk_mq_update_nr_hw_queues+0x124/0x760[EOL] nullb_update_nr_hw_queues+0x71/0xf0 [null_blk][EOL] nullb_device_submit_queues_store+0x92/0x120 [null_blk][EOL][EOL]kobjct_del() was called unconditionally even if sysfs creation failed.[EOL]Fix it by checkig the kobject creation statusbefore deleting it.
