FKIE_CVE-2026-31437

Vulnerability from fkie_nvd - Published: 2026-04-22 14:16 - Updated: 2026-04-23 16:17
Severity ?
Summary
In 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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8
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{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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": "CVE-2026-31437",
  "lastModified": "2026-04-23T16:17:41.280",
  "metrics": {},
  "published": "2026-04-22T14:16:36.980",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Awaiting Analysis"
}


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