ghsa-xv6r-2m8v-f893
Vulnerability from github
Published
2024-03-15 21:30
Modified
2024-03-15 21:30
Details

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

ext4: fix memory leak in ext4_fill_super

Buffer head references must be released before calling kill_bdev(); otherwise the buffer head (and its page referenced by b_data) will not be freed by kill_bdev, and subsequently that bh will be leaked.

If blocksizes differ, sb_set_blocksize() will kill current buffers and page cache by using kill_bdev(). And then super block will be reread again but using correct blocksize this time. sb_set_blocksize() didn't fully free superblock page and buffer head, and being busy, they were not freed and instead leaked.

This can easily be reproduced by calling an infinite loop of:

systemctl start .mount, and systemctl stop .mount

... since systemd creates a cgroup for each slice which it mounts, and the bh leak get amplified by a dying memory cgroup that also never gets freed, and memory consumption is much more easily noticed.

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{
  "affected": [],
  "aliases": [
    "CVE-2021-47119"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-03-15T21:15:07Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix memory leak in ext4_fill_super\n\nBuffer head references must be released before calling kill_bdev();\notherwise the buffer head (and its page referenced by b_data) will not\nbe freed by kill_bdev, and subsequently that bh will be leaked.\n\nIf blocksizes differ, sb_set_blocksize() will kill current buffers and\npage cache by using kill_bdev(). And then super block will be reread\nagain but using correct blocksize this time. sb_set_blocksize() didn\u0027t\nfully free superblock page and buffer head, and being busy, they were\nnot freed and instead leaked.\n\nThis can easily be reproduced by calling an infinite loop of:\n\n  systemctl start \u003cext4_on_lvm\u003e.mount, and\n  systemctl stop \u003cext4_on_lvm\u003e.mount\n\n... since systemd creates a cgroup for each slice which it mounts, and\nthe bh leak get amplified by a dying memory cgroup that also never\ngets freed, and memory consumption is much more easily noticed.",
  "id": "GHSA-xv6r-2m8v-f893",
  "modified": "2024-03-15T21:30:44Z",
  "published": "2024-03-15T21:30:44Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-47119"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/01d349a481f0591230300a9171330136f9159bcd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1385b23396d511d5233b8b921ac3058b3f86a5e1"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/afd09b617db3786b6ef3dc43e28fe728cfea84df"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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