CVE-2024-42102 Revert "mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again"

2024-07-3007:45:58

Linux

www.cve.org

linux kernel

vulnerability resolved

dirty throttling logic

EPSS

Percentile

5.0%

JSON

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

Revert “mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again”

Patch series “mm: Avoid possible overflows in dirty throttling”.

Dirty throttling logic assumes dirty limits in page units fit into
32-bits. This patch series makes sure this is true (see patch 2/2 for
more details).

This patch (of 2):

This reverts commit 9319b647902cbd5cc884ac08a8a6d54ce111fc78.

The commit is broken in several ways. Firstly, the removed (u64) cast
from the multiplication will introduce a multiplication overflow on 32-bit
archs if wb_thresh * bg_thresh >= 1<<32 (which is actually common - the
default settings with 4GB of RAM will trigger this). Secondly, the
div64_u64() is unnecessarily expensive on 32-bit archs. We have
div64_ul() in case we want to be safe & cheap. Thirdly, if dirty
thresholds are larger than 1<<32 pages, then dirty balancing is going to
blow up in many other spectacular ways anyway so trying to fix one
possible overflow is just moot.

CNA Affected

[
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "unaffected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/page-writeback.c"
    ],
    "versions": [
      {
        "version": "c593d26fb5d5",
        "lessThan": "253f9ea7e8e5",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "1f12e4b3284d",
        "lessThan": "23a28f5f3f6c",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "81e7d2530d45",
        "lessThan": "145faa3d0368",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "5099871b3703",
        "lessThan": "2820005edae1",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "16b1025eaa8f",
        "lessThan": "cbbe17a32443",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "ec18ec230301",
        "lessThan": "f6620df12cb6",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "9319b647902c",
        "lessThan": "000099d71648",
        "status": "affected",
        "versionType": "git"
      },
      {
        "version": "9319b647902c",
        "lessThan": "30139c702048",
        "status": "affected",
        "versionType": "git"
      }
    ]
  },
  {
    "product": "Linux",
    "vendor": "Linux",
    "defaultStatus": "affected",
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "programFiles": [
      "mm/page-writeback.c"
    ],
    "versions": [
      {
        "version": "6.8",
        "status": "affected"
      },
      {
        "version": "0",
        "lessThan": "6.8",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "4.19.318",
        "lessThanOrEqual": "4.19.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.4.280",
        "lessThanOrEqual": "5.4.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.10.222",
        "lessThanOrEqual": "5.10.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "5.15.163",
        "lessThanOrEqual": "5.15.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.1.98",
        "lessThanOrEqual": "6.1.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.6.39",
        "lessThanOrEqual": "6.6.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.9.9",
        "lessThanOrEqual": "6.9.*",
        "status": "unaffected",
        "versionType": "custom"
      },
      {
        "version": "6.10",
        "lessThanOrEqual": "*",
        "status": "unaffected",
        "versionType": "original_commit_for_fix"
      }
    ]
  }
]