GHSA-R9WM-P769-97J8
Vulnerability from github – Published: 2026-08-15 06:32 – Updated: 2026-08-17 06:33In the Linux kernel, the following vulnerability has been resolved:
iomap: guard io_size EOF trim against concurrent truncate underflow
iomap: fix zero padding data issue in concurrent append writes changed ioend accounting so that io_size tracks only valid data within EOF. This trims io_size when a writeback range extends past end_pos:
ioend->io_size += map_len;
if (ioend->io_offset + ioend->io_size > end_pos)
ioend->io_size = end_pos - ioend->io_offset;
However, if end_pos ends up below ioend->io_offset, the subtraction becomes negative and is stored in size_t io_size, causing an unsigned wrap to a huge value. This can happen when writeback continues past byte-level EOF up to a block-aligned range, or when a concurrent truncate shrinks the file after end_pos was sampled in iomap_writeback_handle_eof().
A wrapped io_size can mislead append detection and corrupt completion-time size handling, since filesystem end_io paths consume io_size for decisions such as on-disk EOF updates and unwritten/COW completion ranges.
Fix this by clamping io_size to zero when EOF has moved to or before the ioend start offset. This preserves the original intent of trimming io_size to valid in-EOF data while avoiding the underflow.
{
"affected": [],
"aliases": [
"CVE-2026-72367"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-15T06:22:10Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\niomap: guard io_size EOF trim against concurrent truncate underflow\n\niomap: fix zero padding data issue in concurrent append writes\nchanged ioend accounting so that io_size tracks only valid data\nwithin EOF. This trims io_size when a writeback range extends\npast end_pos:\n\n ioend-\u003eio_size += map_len;\n if (ioend-\u003eio_offset + ioend-\u003eio_size \u003e end_pos)\n ioend-\u003eio_size = end_pos - ioend-\u003eio_offset;\n\nHowever, if end_pos ends up below ioend-\u003eio_offset, the subtraction\nbecomes negative and is stored in size_t io_size, causing an unsigned\nwrap to a huge value. This can happen when writeback continues past\nbyte-level EOF up to a block-aligned range, or when a concurrent\ntruncate shrinks the file after end_pos was sampled in\niomap_writeback_handle_eof().\n\nA wrapped io_size can mislead append detection and corrupt\ncompletion-time size handling, since filesystem end_io paths consume\nio_size for decisions such as on-disk EOF updates and unwritten/COW\ncompletion ranges.\n\nFix this by clamping io_size to zero when EOF has moved to or before\nthe ioend start offset. This preserves the original intent of trimming\nio_size to valid in-EOF data while avoiding the underflow.",
"id": "GHSA-r9wm-p769-97j8",
"modified": "2026-08-17T06:33:25Z",
"published": "2026-08-15T06:32:21Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-72367"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1f38f65bf965fce9aa159d45c5347538f56c5973"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/55ec50d046c03b3724741957f7b007856e36dbe7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7f7780abb4c0fdc9a2603aea8e985ff14ee900e0"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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