GHSA-H3HR-9QQW-CVG3
Vulnerability from github – Published: 2026-04-22 15:31 – Updated: 2026-05-20 00:31In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry
When a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path in netfs_unbuffered_write() unconditionally calls stream->prepare_write() without checking if it is NULL.
Filesystems such as 9P do not set the prepare_write operation, so stream->prepare_write remains NULL. When get_user_pages() fails with -EFAULT and the subrequest is flagged for retry, this results in a NULL pointer dereference at fs/netfs/direct_write.c:189.
Fix this by mirroring the pattern already used in write_retry.c: if stream->prepare_write is NULL, skip renegotiation and directly reissue the subrequest via netfs_reissue_write(), which handles iterator reset, IN_PROGRESS flag, stats update and reissue internally.
{
"affected": [],
"aliases": [
"CVE-2026-31437"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-04-22T14:16:36Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry\n\nWhen a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path\nin netfs_unbuffered_write() unconditionally calls stream-\u003eprepare_write()\nwithout checking if it is NULL.\n\nFilesystems such as 9P do not set the prepare_write operation, so\nstream-\u003eprepare_write remains NULL. When get_user_pages() fails with\n-EFAULT and the subrequest is flagged for retry, this results in a NULL\npointer dereference at fs/netfs/direct_write.c:189.\n\nFix this by mirroring the pattern already used in write_retry.c: if\nstream-\u003eprepare_write is NULL, skip renegotiation and directly reissue\nthe subrequest via netfs_reissue_write(), which handles iterator reset,\nIN_PROGRESS flag, stats update and reissue internally.",
"id": "GHSA-h3hr-9qqw-cvg3",
"modified": "2026-05-20T00:31:40Z",
"published": "2026-04-22T15:31:40Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31437"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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