GHSA-C7GF-37RM-RPG6

Vulnerability from github – Published: 2026-05-27 15:33 – Updated: 2026-05-27 15:33
VLAI
Details

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

gfs2: Fix use-after-free in iomap inline data write path

The inline data buffer head (dibh) is being released prematurely in gfs2_iomap_begin() via release_metapath() while iomap->inline_data still points to dibh->b_data. This causes a use-after-free when iomap_write_end_inline() later attempts to write to the inline data area.

The bug sequence: 1. gfs2_iomap_begin() calls gfs2_meta_inode_buffer() to read inode metadata into dibh 2. Sets iomap->inline_data = dibh->b_data + sizeof(struct gfs2_dinode) 3. Calls release_metapath() which calls brelse(dibh), dropping refcount to 0 4. kswapd reclaims the page (~39ms later in the syzbot report) 5. iomap_write_end_inline() tries to memcpy() to iomap->inline_data 6. KASAN detects use-after-free write to freed memory

Fix by storing dibh in iomap->private and incrementing its refcount with get_bh() in gfs2_iomap_begin(). The buffer is then properly released in gfs2_iomap_end() after the inline write completes, ensuring the page stays alive for the entire iomap operation.

Note: A C reproducer is not available for this issue. The fix is based on analysis of the KASAN report and code review showing the buffer head is freed before use.

[agruenba: Take buffer head reference in gfs2_iomap_begin() to avoid leaks in gfs2_iomap_get() and gfs2_iomap_alloc().]

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{
  "affected": [],
  "aliases": [
    "CVE-2026-45984"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-27T14:17:15Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ngfs2: Fix use-after-free in iomap inline data write path\n\nThe inline data buffer head (dibh) is being released prematurely in\ngfs2_iomap_begin() via release_metapath() while iomap-\u003einline_data\nstill points to dibh-\u003eb_data. This causes a use-after-free when\niomap_write_end_inline() later attempts to write to the inline data\narea.\n\nThe bug sequence:\n1. gfs2_iomap_begin() calls gfs2_meta_inode_buffer() to read inode\n   metadata into dibh\n2. Sets iomap-\u003einline_data = dibh-\u003eb_data + sizeof(struct gfs2_dinode)\n3. Calls release_metapath() which calls brelse(dibh), dropping refcount\n   to 0\n4. kswapd reclaims the page (~39ms later in the syzbot report)\n5. iomap_write_end_inline() tries to memcpy() to iomap-\u003einline_data\n6. KASAN detects use-after-free write to freed memory\n\nFix by storing dibh in iomap-\u003eprivate and incrementing its refcount\nwith get_bh() in gfs2_iomap_begin(). The buffer is then properly\nreleased in gfs2_iomap_end() after the inline write completes,\nensuring the page stays alive for the entire iomap operation.\n\nNote: A C reproducer is not available for this issue. The fix is based\non analysis of the KASAN report and code review showing the buffer head\nis freed before use.\n\n[agruenba: Take buffer head reference in gfs2_iomap_begin() to avoid\nleaks in gfs2_iomap_get() and gfs2_iomap_alloc().]",
  "id": "GHSA-c7gf-37rm-rpg6",
  "modified": "2026-05-27T15:33:19Z",
  "published": "2026-05-27T15:33:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45984"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1403989d1b502f4a2c0d0b42ccf1c25748442eff"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1cae1bafdf9caa9b462b19af06b1a06902e4e142"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6d76febba07c40bcf358f63216d36ea68cf1c215"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/764c3c84b5683e608f43735c803a5f415046686c"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/815ddd27c0c7171a99fe802fdb19098ddef8b19d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/87d4954b5c59735a99ea98cb208d47130f6dce7d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d87268326b277af3665237ac76a73dd9fa8e21b4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/faddeb848305e79db89ee0479bb0e33380656321"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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