linux-cve-announce - CVE-2023-53783: blk-iocost: fix divide by 0 error in calc

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Message-ID: <2025120939-CVE-2023-53783-4c33@gregkh>
Date: Tue,  9 Dec 2025 09:02:04 +0900
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53783: blk-iocost: fix divide by 0 error in calc_lcoefs()

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

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

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

blk-iocost: fix divide by 0 error in calc_lcoefs()

echo max of u64 to cost.model can cause divide by 0 error.

  # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model

  divide error: 0000 [#1] PREEMPT SMP
  RIP: 0010:calc_lcoefs+0x4c/0xc0
  Call Trace:
   <TASK>
   ioc_refresh_params+0x2b3/0x4f0
   ioc_cost_model_write+0x3cb/0x4c0
   ? _copy_from_iter+0x6d/0x6c0
   ? kernfs_fop_write_iter+0xfc/0x270
   cgroup_file_write+0xa0/0x200
   kernfs_fop_write_iter+0x17d/0x270
   vfs_write+0x414/0x620
   ksys_write+0x73/0x160
   __x64_sys_write+0x1e/0x30
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x63/0xcd

calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL,
overflow would happen if bps plus IOC_PAGE_SIZE is greater than
ULLONG_MAX, it can cause divide by 0 error.

Fix the problem by setting basecost

The Linux kernel CVE team has assigned CVE-2023-53783 to this issue.


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

	Fixed in 5.4.235 with commit 9e8bf9f95f7a299fa9ea45b678d001806ad5e12c
	Fixed in 5.10.173 with commit 6e291810fe83a384700eb24a1f714966391ed562
	Fixed in 5.15.99 with commit 3538ade9d8c2ba41088e395de916f2599fadba8f
	Fixed in 6.1.16 with commit bf8eb1fd6110871e6232e8e7efe399276ef7e6f6
	Fixed in 6.2.3 with commit b96d7b4a9745fbd0c8384608ceb1f50415e862fa
	Fixed in 6.3 with commit 984af1e66b4126cf145153661cc24c213e2ec231

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-2023-53783
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/blk-iocost.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/9e8bf9f95f7a299fa9ea45b678d001806ad5e12c
	https://git.kernel.org/stable/c/6e291810fe83a384700eb24a1f714966391ed562
	https://git.kernel.org/stable/c/3538ade9d8c2ba41088e395de916f2599fadba8f
	https://git.kernel.org/stable/c/bf8eb1fd6110871e6232e8e7efe399276ef7e6f6
	https://git.kernel.org/stable/c/b96d7b4a9745fbd0c8384608ceb1f50415e862fa
	https://git.kernel.org/stable/c/984af1e66b4126cf145153661cc24c213e2ec231