{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-39723",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-39723"
  ],
  "published": "2025-09-05T17:22:05Z",
  "summary": "netfs: Fix unbuffered write error handling",
  "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.",
  "affected": [
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        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
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        "1:6.12.25-1+rpt1",
        "1:6.12.34-1+rpt1~bookworm"
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      "ecosystem_specific": {
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          },
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            "binary_version": "1:6.12.20-1+rpt1~bpo12+1"
          },
          {
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            "binary_version": "1:6.12.20-1+rpt1~bpo12+1"
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            "binary_version": "1:6.12.20-1+rpt1~bpo12+1"
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            "binary_version": "1:6.12.25-1+rpt1"
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            "binary_version": "1:6.12.34-1+rpt1~bookworm"
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            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.44"
          },
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            "linux_commit": "3dd2c2c507c271d411fab2e82a2b3b7e0b6d3f16",
            "upstream_version": "6.12.25",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.44"
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          "1:6.12.34-1+rpt1~bookworm": {
            "linux_commit": "8f77e03530f65209a377d25023e912b288e039cd",
            "upstream_version": "6.12.34",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.12.44"
          }
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    },
    {
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        "ecosystem": "Raspberry Pi OS:13",
        "name": "linux"
      },
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        "1:6.12.19-1+rpt1",
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  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-39723"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f08c80af3c9a9849cd178b4843b7c01d103506a1"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/387164a2b97e1f5404c6d0049a7409bac7d2bc5b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/a3de58b12ce074ec05b8741fa28d62ccb1070468"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-08-05T12:19:11Z"
  }
}