{
  "schema_version": "1.4.0",
  "id": "GHSA-6r55-jr8w-3x3r",
  "modified": "2025-09-05T18:31:27Z",
  "published": "2025-09-05T18:31:27Z",
  "aliases": [
    "CVE-2025-39723"
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix unbuffered write error handling\n\nIf all the subrequests in an unbuffered write stream fail, the subrequest\ncollector doesn't update the stream->transferred value and it retains its\ninitial LONG_MAX value.  Unfortunately, if all active streams fail, then we\ntake the smallest value of { LONG_MAX, LONG_MAX, ... } as the value to set\nin wreq->transferred - which is then returned from ->write_iter().\n\nLONG_MAX was chosen as the initial value so that all the streams can be\nquickly assessed by taking the smallest value of all stream->transferred -\nbut this only works if we've set any of them.\n\nFix this by adding a flag to indicate whether the value in\nstream->transferred is valid and checking that when we integrate the\nvalues.  stream->transferred can then be initialised to zero.\n\nThis was found by running the generic/750 xfstest against cifs with\ncache=none.  It splices data to the target file.  Once (if) it has used up\nall the available scratch space, the writes start failing with ENOSPC.\nThis causes ->write_iter() to fail.  However, it was returning\nwreq->transferred, i.e. LONG_MAX, rather than an error (because it thought\nthe amount transferred was non-zero) and iter_file_splice_write() would\nthen try to clean up that amount of pipe bufferage - leading to an oops\nwhen it overran.  The kernel log showed:\n\n    CIFS: VFS: Send error in write = -28\n\nfollowed by:\n\n    BUG: kernel NULL pointer dereference, address: 0000000000000008\n\nwith:\n\n    RIP: 0010:iter_file_splice_write+0x3a4/0x520\n    do_splice+0x197/0x4e0\n\nor:\n\n    RIP: 0010:pipe_buf_release (include/linux/pipe_fs_i.h:282)\n    iter_file_splice_write (fs/splice.c:755)\n\nAlso put a warning check into splice to announce if ->write_iter() returned\nthat it had written more than it was asked to.",
  "severity": [],
  "affected": [],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39723"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/387164a2b97e1f5404c6d0049a7409bac7d2bc5b"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a3de58b12ce074ec05b8741fa28d62ccb1070468"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f08c80af3c9a9849cd178b4843b7c01d103506a1"
    }
  ],
  "database_specific": {
    "cwe_ids": [],
    "severity": null,
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-05T18:15:50Z"
  }
}