CVE-2022-49902

In the Linux kernel, the following vulnerability has been resolved:

block: Fix possible memory leak for rqwb on adddisk failure

kmemleak reported memory leaks in deviceadddisk():

kmemleak: 3 new suspected memory leaks

unreferenced object 0xffff88800f420800 (size 512): comm "modprobe", pid 4275, jiffies 4295639067 (age 223.512s) hex dump (first 32 bytes): 04 00 00 00 08 00 00 00 01 00 00 00 00 00 00 00 ................ 00 e1 f5 05 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000d3662699>] kmalloctrace+0x26/0x60 [<00000000edc7aadc>] wbtinit+0x50/0x6f0 [<0000000069601d16>] wbtenabledefault+0x157/0x1c0 [<0000000028fc393f>] blkregisterqueue+0x2a4/0x420 [<000000007345a042>] deviceadddisk+0x6fd/0xe40 [<0000000060e6aab0>] nbddevadd+0x828/0xbf0 [nbd] ...

It is because the memory allocated in wbtenabledefault() is not released in deviceadddisk() error path. Normally, these memory are freed in:

delgendisk() rqqosexit() rqos->ops->exit(rqos); wbtexit()

So rqqosexit() is called to free the rqwb memory for wbtinit(). However in the error path of deviceadddisk(), only blkunregisterqueue() is called and make rq_wb memory leaked.

Add rqqosexit() to the error path to fix it.