linux-cve-announce - CVE-2022-49902: block: Fix possible memory leak for rq_wb on add

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Message-ID: <2025050102-CVE-2022-49902-59fe@gregkh>
Date: Thu,  1 May 2025 16:11:32 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49902: block: Fix possible memory leak for rq_wb on add_disk failure

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

block: Fix possible memory leak for rq_wb on add_disk failure

kmemleak reported memory leaks in device_add_disk():

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>] kmalloc_trace+0x26/0x60
    [<00000000edc7aadc>] wbt_init+0x50/0x6f0
    [<0000000069601d16>] wbt_enable_default+0x157/0x1c0
    [<0000000028fc393f>] blk_register_queue+0x2a4/0x420
    [<000000007345a042>] device_add_disk+0x6fd/0xe40
    [<0000000060e6aab0>] nbd_dev_add+0x828/0xbf0 [nbd]
    ...

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

del_gendisk()
  rq_qos_exit()
    rqos->ops->exit(rqos);
      wbt_exit()

So rq_qos_exit() is called to free the rq_wb memory for wbt_init().
However in the error path of device_add_disk(), only
blk_unregister_queue() is called and make rq_wb memory leaked.

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

The Linux kernel CVE team has assigned CVE-2022-49902 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.15 with commit 83cbce9574462c6b4eed6797bdaf18fae6859ab3 and fixed in 5.15.78 with commit 4e68c5da60cd79950bd56287ae80b39d6261f995
	Issue introduced in 5.15 with commit 83cbce9574462c6b4eed6797bdaf18fae6859ab3 and fixed in 6.0.8 with commit 528677d3b4af985445bd4ac667485ded1ed11220
	Issue introduced in 5.15 with commit 83cbce9574462c6b4eed6797bdaf18fae6859ab3 and fixed in 6.1 with commit fa81cbafbf5764ad5053512152345fab37a1fe18

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49902
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	block/genhd.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/4e68c5da60cd79950bd56287ae80b39d6261f995
	https://git.kernel.org/stable/c/528677d3b4af985445bd4ac667485ded1ed11220
	https://git.kernel.org/stable/c/fa81cbafbf5764ad5053512152345fab37a1fe18