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

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-05-23 16:01
VLAI
Title
fs/notify: call exportfs_encode_fid with s_umount
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 CPE status
Linux Linux Affected: a1a541fbfa7e97c1100144db34b57553d7164ce5 , < 950b604384fd75d62e860bec7135b2b62eb4d508 (git)
Affected: f0c0ac84de17c37e6e84da65fb920f91dada55ad , < bc1c6b803e14ea2b8f7e33b7164013f666ceb656 (git)
Affected: 3c7c90274ae339e1ad443c9be1c67a20b80b9c76 , < 3f307a9f7a7a2822e38ac451b73e2244e7279496 (git)
Affected: c45beebfde34aa71afbc48b2c54cdda623515037 , < d1894bc542becb0fda61e7e513b09523cab44030 (git)
Affected: c45beebfde34aa71afbc48b2c54cdda623515037 , < a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a (git)
Affected: 6.6.72 , < 6.6.73 (semver)
Affected: 6.6.74 , < 6.6.115 (semver)
Affected: 6.12.10 , < 6.12.56 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (semver)
Unaffected: 6.6.73 , ≤ 6.6.* (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)
guessed Create a notification for this product.
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              "negate": false,
              "operator": "OR"
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      "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/"
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        "dateUpdated": "2026-05-23T16:01:45.934Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a"
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      "title": "fs/notify: call exportfs_encode_fid with s_umount",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40237",
    "datePublished": "2025-12-04T15:31:27.325Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2026-05-23T16:01:45.934Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "cve": "CVE-2025-40237",
      "date": "2026-09-16",
      "epss": "0.00201",
      "percentile": "0.102"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40237\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-04T16:16:16.697\",\"lastModified\":\"2026-06-17T09:21:30.407\",\"vulnStatus\":\"Deferred\",\"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/\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/notify/fdinfo.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"a1a541fbfa7e97c1100144db34b57553d7164ce5\",\"lessThan\":\"950b604384fd75d62e860bec7135b2b62eb4d508\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"f0c0ac84de17c37e6e84da65fb920f91dada55ad\",\"lessThan\":\"bc1c6b803e14ea2b8f7e33b7164013f666ceb656\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"3c7c90274ae339e1ad443c9be1c67a20b80b9c76\",\"lessThan\":\"3f307a9f7a7a2822e38ac451b73e2244e7279496\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c45beebfde34aa71afbc48b2c54cdda623515037\",\"lessThan\":\"d1894bc542becb0fda61e7e513b09523cab44030\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"c45beebfde34aa71afbc48b2c54cdda623515037\",\"lessThan\":\"a7c4bb43bfdc2b9f06ee9d036028ed13a83df42a\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"6.6.72\",\"lessThan\":\"6.6.73\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.6.74\",\"lessThan\":\"6.6.115\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"6.12.10\",\"lessThan\":\"6.12.56\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/notify/fdinfo.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"6.13\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"6.13\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.73\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.115\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.56\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.17.6\",\"lessThanOrEqual\":\"6.17.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/3f307a9f7a7a2822e38ac451b73e2244e7279496\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/950b604384fd75d62e860bec7135b2b62eb4d508\",\"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\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-24T14:59:04+00:00",
      "cve": "CVE-2025-40237",
      "id": "CVE-2025-40237",
      "initial_release_date": "2025-12-04T00:00:00+00:00",
      "product_status:fixed": "309",
      "product_status:known_affected": "108",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fs/notify: call exportfs_encode_fid with s_umount",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40237.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-11T01:54:37Z",
      "cve": "CVE-2025-40237",
      "id": "CVE-2025-40237",
      "initial_release_date": "2025-12-05T00:25:47Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "394",
      "product_status:known_not_affected": "538",
      "product_status:recommended": "214",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40237",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40237.json",
      "version": "29"
    }
  }
}



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