cve-2025-21643
Vulnerability from cvelistv5
Published
2025-01-19 10:17
Modified
2025-01-20 06:30
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: netfs: Fix kernel async DIO Netfslib needs to be able to handle kernel-initiated asynchronous DIO that is supplied with a bio_vec[] array. Currently, because of the async flag, this gets passed to netfs_extract_user_iter() which throws a warning and fails because it only handles IOVEC and UBUF iterators. This can be triggered through a combination of cifs and a loopback blockdev with something like: mount //my/cifs/share /foo dd if=/dev/zero of=/foo/m0 bs=4K count=1K losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0 echo hello >/dev/loop2046 This causes the following to appear in syslog: WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs] and the write to fail. Fix this by removing the check in netfs_unbuffered_write_iter_locked() that causes async kernel DIO writes to be handled as userspace writes. Note that this change relies on the kernel caller maintaining the existence of the bio_vec array (or kvec[] or folio_queue) until the op is complete.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3f6bc9e3ab9b127171d39f9ac6eca1abb693b731
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9f3a265836844eda30bf34c2584b8011fd4f0f49
Impacted products
Vendor Product Version
Linux Linux Version: 153a9961b551101cd38e94e26cd92fbfd198b19b
Version: 153a9961b551101cd38e94e26cd92fbfd198b19b
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   Linux Linux Version: 6.8
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{
   containers: {
      cna: {
         affected: [
            {
               defaultStatus: "unaffected",
               product: "Linux",
               programFiles: [
                  "fs/netfs/direct_write.c",
               ],
               repo: "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               vendor: "Linux",
               versions: [
                  {
                     lessThan: "9f3a265836844eda30bf34c2584b8011fd4f0f49",
                     status: "affected",
                     version: "153a9961b551101cd38e94e26cd92fbfd198b19b",
                     versionType: "git",
                  },
                  {
                     lessThan: "3f6bc9e3ab9b127171d39f9ac6eca1abb693b731",
                     status: "affected",
                     version: "153a9961b551101cd38e94e26cd92fbfd198b19b",
                     versionType: "git",
                  },
               ],
            },
            {
               defaultStatus: "affected",
               product: "Linux",
               programFiles: [
                  "fs/netfs/direct_write.c",
               ],
               repo: "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
               vendor: "Linux",
               versions: [
                  {
                     status: "affected",
                     version: "6.8",
                  },
                  {
                     lessThan: "6.8",
                     status: "unaffected",
                     version: "0",
                     versionType: "semver",
                  },
                  {
                     lessThanOrEqual: "6.12.*",
                     status: "unaffected",
                     version: "6.12.10",
                     versionType: "semver",
                  },
                  {
                     lessThanOrEqual: "*",
                     status: "unaffected",
                     version: "6.13",
                     versionType: "original_commit_for_fix",
                  },
               ],
            },
         ],
         descriptions: [
            {
               lang: "en",
               value: "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfs: Fix kernel async DIO\n\nNetfslib needs to be able to handle kernel-initiated asynchronous DIO that\nis supplied with a bio_vec[] array.  Currently, because of the async flag,\nthis gets passed to netfs_extract_user_iter() which throws a warning and\nfails because it only handles IOVEC and UBUF iterators.  This can be\ntriggered through a combination of cifs and a loopback blockdev with\nsomething like:\n\n        mount //my/cifs/share /foo\n        dd if=/dev/zero of=/foo/m0 bs=4K count=1K\n        losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0\n        echo hello >/dev/loop2046\n\nThis causes the following to appear in syslog:\n\n        WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs]\n\nand the write to fail.\n\nFix this by removing the check in netfs_unbuffered_write_iter_locked() that\ncauses async kernel DIO writes to be handled as userspace writes.  Note\nthat this change relies on the kernel caller maintaining the existence of\nthe bio_vec array (or kvec[] or folio_queue) until the op is complete.",
            },
         ],
         providerMetadata: {
            dateUpdated: "2025-01-20T06:30:01.152Z",
            orgId: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            shortName: "Linux",
         },
         references: [
            {
               url: "https://git.kernel.org/stable/c/9f3a265836844eda30bf34c2584b8011fd4f0f49",
            },
            {
               url: "https://git.kernel.org/stable/c/3f6bc9e3ab9b127171d39f9ac6eca1abb693b731",
            },
         ],
         title: "netfs: Fix kernel async DIO",
         x_generator: {
            engine: "bippy-5f407fcff5a0",
         },
      },
   },
   cveMetadata: {
      assignerOrgId: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      assignerShortName: "Linux",
      cveId: "CVE-2025-21643",
      datePublished: "2025-01-19T10:17:59.820Z",
      dateReserved: "2024-12-29T08:45:45.727Z",
      dateUpdated: "2025-01-20T06:30:01.152Z",
      state: "PUBLISHED",
   },
   dataType: "CVE_RECORD",
   dataVersion: "5.1",
   "vulnerability-lookup:meta": {
      nvd: "{\"cve\":{\"id\":\"CVE-2025-21643\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-01-19T11:15:09.870\",\"lastModified\":\"2025-01-19T11:15:09.870\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnetfs: Fix kernel async DIO\\n\\nNetfslib needs to be able to handle kernel-initiated asynchronous DIO that\\nis supplied with a bio_vec[] array.  Currently, because of the async flag,\\nthis gets passed to netfs_extract_user_iter() which throws a warning and\\nfails because it only handles IOVEC and UBUF iterators.  This can be\\ntriggered through a combination of cifs and a loopback blockdev with\\nsomething like:\\n\\n        mount //my/cifs/share /foo\\n        dd if=/dev/zero of=/foo/m0 bs=4K count=1K\\n        losetup --sector-size 4096 --direct-io=on /dev/loop2046 /foo/m0\\n        echo hello >/dev/loop2046\\n\\nThis causes the following to appear in syslog:\\n\\n        WARNING: CPU: 2 PID: 109 at fs/netfs/iterator.c:50 netfs_extract_user_iter+0x170/0x250 [netfs]\\n\\nand the write to fail.\\n\\nFix this by removing the check in netfs_unbuffered_write_iter_locked() that\\ncauses async kernel DIO writes to be handled as userspace writes.  Note\\nthat this change relies on the kernel caller maintaining the existence of\\nthe bio_vec array (or kvec[] or folio_queue) until the op is complete.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3f6bc9e3ab9b127171d39f9ac6eca1abb693b731\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9f3a265836844eda30bf34c2584b8011fd4f0f49\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
   },
}


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