CVE-2025-40237 (GCVE-0-2025-40237)

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2025-12-04 15:31
VLAI?
Summary
In the Linux kernel, the following vulnerability has been resolved: fs/notify: call exportfs_encode_fid with s_umount Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL | | vfs_read() | inotify_fdinfo() | * inode get from mark * | show_mark_fhandle(m, inode) | exportfs_encode_fid(inode, ..) | ovl_encode_fh(inode, ..) | ovl_check_encode_origin(inode) | * deref i_sb->s_root * | | v fsnotify_sb_delete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) <snip registers, unreliable trace> [ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240 IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path. Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: f0c0ac84de17c37e6e84da65fb920f91dada55ad , < bc1c6b803e14ea2b8f7e33b7164013f666ceb656 (git)
Affected: 3c7c90274ae339e1ad443c9be1c67a20b80b9c76 , < 3f307a9f7a7a2822e38ac451b73e2244e7279496 (git)
Affected: c45beebfde34aa71afbc48b2c54cdda623515037 , < d1894bc542becb0fda61e7e513b09523cab44030 (git)
Affected: c45beebfde34aa71afbc48b2c54cdda623515037 , < a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a (git)
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    Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.6.115 , ≤ 6.6.* (semver)
Unaffected: 6.12.56 , ≤ 6.12.* (semver)
Unaffected: 6.17.6 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/notify/fdinfo.c"
          ],
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          "vendor": "Linux",
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          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/notify/fdinfo.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "6.13"
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              "lessThan": "6.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
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              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.56",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.6",
              "versionType": "semver"
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              "lessThanOrEqual": "*",
              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.115",
                  "versionStartIncluding": "6.6.74",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.56",
                  "versionStartIncluding": "6.12.10",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.6",
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/notify: call exportfs_encode_fid with s_umount\n\nCalling intotify_show_fdinfo() on fd watching an overlayfs inode, while\nthe overlayfs is being unmounted, can lead to dereferencing NULL ptr.\n\nThis issue was found by syzkaller.\n\nRace Condition Diagram:\n\nThread 1                           Thread 2\n--------                           --------\n\ngeneric_shutdown_super()\n shrink_dcache_for_umount\n  sb-\u003es_root = NULL\n\n                    |\n                    |             vfs_read()\n                    |              inotify_fdinfo()\n                    |               * inode get from mark *\n                    |               show_mark_fhandle(m, inode)\n                    |                exportfs_encode_fid(inode, ..)\n                    |                 ovl_encode_fh(inode, ..)\n                    |                  ovl_check_encode_origin(inode)\n                    |                   * deref i_sb-\u003es_root *\n                    |\n                    |\n                    v\n fsnotify_sb_delete(sb)\n\nWhich then leads to:\n\n[   32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[   32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]\n[   32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none)\n\n\u003csnip registers, unreliable trace\u003e\n\n[   32.143353] Call Trace:\n[   32.143732]  ovl_encode_fh+0xd5/0x170\n[   32.144031]  exportfs_encode_inode_fh+0x12f/0x300\n[   32.144425]  show_mark_fhandle+0xbe/0x1f0\n[   32.145805]  inotify_fdinfo+0x226/0x2d0\n[   32.146442]  inotify_show_fdinfo+0x1c5/0x350\n[   32.147168]  seq_show+0x530/0x6f0\n[   32.147449]  seq_read_iter+0x503/0x12a0\n[   32.148419]  seq_read+0x31f/0x410\n[   32.150714]  vfs_read+0x1f0/0x9e0\n[   32.152297]  ksys_read+0x125/0x240\n\nIOW ovl_check_encode_origin derefs inode-\u003ei_sb-\u003es_root, after it was set\nto NULL in the unmount path.\n\nFix it by protecting calling exportfs_encode_fid() from\nshow_mark_fhandle() with s_umount lock.\n\nThis form of fix was suggested by Amir in [1].\n\n[1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-04T15:31:27.325Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656"
        },
        {
          "url": "https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496"
        },
        {
          "url": "https://git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030"
        },
        {
          "url": "https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"
        }
      ],
      "title": "fs/notify: call exportfs_encode_fid with s_umount",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40237",
    "datePublished": "2025-12-04T15:31:27.325Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2025-12-04T15:31:27.325Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40237\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-04T16:16:16.697\",\"lastModified\":\"2025-12-04T17:15:08.283\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nfs/notify: call exportfs_encode_fid with s_umount\\n\\nCalling intotify_show_fdinfo() on fd watching an overlayfs inode, while\\nthe overlayfs is being unmounted, can lead to dereferencing NULL ptr.\\n\\nThis issue was found by syzkaller.\\n\\nRace Condition Diagram:\\n\\nThread 1                           Thread 2\\n--------                           --------\\n\\ngeneric_shutdown_super()\\n shrink_dcache_for_umount\\n  sb-\u003es_root = NULL\\n\\n                    |\\n                    |             vfs_read()\\n                    |              inotify_fdinfo()\\n                    |               * inode get from mark *\\n                    |               show_mark_fhandle(m, inode)\\n                    |                exportfs_encode_fid(inode, ..)\\n                    |                 ovl_encode_fh(inode, ..)\\n                    |                  ovl_check_encode_origin(inode)\\n                    |                   * deref i_sb-\u003es_root *\\n                    |\\n                    |\\n                    v\\n fsnotify_sb_delete(sb)\\n\\nWhich then leads to:\\n\\n[   32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\\n[   32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]\\n[   32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none)\\n\\n\u003csnip registers, unreliable trace\u003e\\n\\n[   32.143353] Call Trace:\\n[   32.143732]  ovl_encode_fh+0xd5/0x170\\n[   32.144031]  exportfs_encode_inode_fh+0x12f/0x300\\n[   32.144425]  show_mark_fhandle+0xbe/0x1f0\\n[   32.145805]  inotify_fdinfo+0x226/0x2d0\\n[   32.146442]  inotify_show_fdinfo+0x1c5/0x350\\n[   32.147168]  seq_show+0x530/0x6f0\\n[   32.147449]  seq_read_iter+0x503/0x12a0\\n[   32.148419]  seq_read+0x31f/0x410\\n[   32.150714]  vfs_read+0x1f0/0x9e0\\n[   32.152297]  ksys_read+0x125/0x240\\n\\nIOW ovl_check_encode_origin derefs inode-\u003ei_sb-\u003es_root, after it was set\\nto NULL in the unmount path.\\n\\nFix it by protecting calling exportfs_encode_fid() from\\nshow_mark_fhandle() with s_umount lock.\\n\\nThis form of fix was suggested by Amir in [1].\\n\\n[1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bc1c6b803e14ea2b8f7e33b7164013f666ceb656\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d1894bc542becb0fda61e7e513b09523cab44030\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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