CVE-2025-40072

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: fanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing The function do_fanotify_mark() does not validate if mnt_ns_from_dentry() returns NULL before dereferencing mntns->user_ns. This causes a NULL pointer dereference in do_fanotify_mark() if the path is not a mount namespace object. Fix this by checking mnt_ns_from_dentry()'s return value before dereferencing it. Before the patch $ gcc fanotify_nullptr.c -o fanotify_nullptr $ mkdir A $ ./fanotify_nullptr Fanotify fd: 3 fanotify_mark: Operation not permitted $ unshare -Urm Fanotify fd: 3 Killed int main(void){ int ffd; ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0); if(ffd < 0){ perror("fanotify_init"); exit(EXIT_FAILURE); } printf("Fanotify fd: %d\n",ffd); if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS, FAN_MNT_ATTACH, AT_FDCWD, "A") < 0){ perror("fanotify_mark"); exit(EXIT_FAILURE); } return 0; } After the patch $ gcc fanotify_nullptr.c -o fanotify_nullptr $ mkdir A $ ./fanotify_nullptr Fanotify fd: 3 fanotify_mark: Operation not permitted $ unshare -Urm Fanotify fd: 3 fanotify_mark: Invalid argument [ 25.694973] BUG: kernel NULL pointer dereference, address: 0000000000000038 [ 25.695006] #PF: supervisor read access in kernel mode [ 25.695012] #PF: error_code(0x0000) - not-present page [ 25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0 [ 25.695025] Oops: Oops: 0000 [#1] SMP NOPTI [ 25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt Not tainted 6.17.0-rc4 #1 PREEMPT(lazy) [ 25.695040] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 [ 25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950 [ 25.695066] Code: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54 24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b 5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28 85 c9 [ 25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203 [ 25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220 [ 25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180 [ 25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000 [ 25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7 [ 25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0 [ 25.695154] FS: 00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000) knlGS:0000000000000000 [ 25.695162] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0 [ 25.695201] Call Trace: [ 25.695209] <TASK> [ 25.695215] __x64_sys_fanotify_mark+0x1f/0x30 [ 25.695222] do_syscall_64+0x82/0x2c0 ...

Severity

Not scored

CVSS score

Not available

Vulnerability status

Deferred

Source identifier

416baaa9-dc9f-4396-8d5f-8c081fb06d67

Published

2025-10-28 12:15:41.723000

Last modified

2026-10-19 21:10:00.160000

View original CVE JSON

{
  "id": "CVE-2025-40072",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-10-28T12:15:41.723",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfanotify: Validate the return value of mnt_ns_from_dentry() before dereferencing\n\nThe function do_fanotify_mark() does not validate if\nmnt_ns_from_dentry() returns NULL before dereferencing mntns->user_ns.\nThis causes a NULL pointer dereference in do_fanotify_mark() if the\npath is not a mount namespace object.\n\nFix this by checking mnt_ns_from_dentry()'s return value before\ndereferencing it.\n\nBefore the patch\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operation not permitted\n$ unshare -Urm\nFanotify fd: 3\nKilled\n\nint main(void){\n    int ffd;\n    ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0);\n    if(ffd < 0){\n        perror(\"fanotify_init\");\n        exit(EXIT_FAILURE);\n    }\n\n    printf(\"Fanotify fd: %d\\n\",ffd);\n\n    if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS,\nFAN_MNT_ATTACH, AT_FDCWD, \"A\") < 0){\n        perror(\"fanotify_mark\");\n        exit(EXIT_FAILURE);\n    }\n\nreturn 0;\n}\n\nAfter the patch\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operation not permitted\n$ unshare -Urm\nFanotify fd: 3\nfanotify_mark: Invalid argument\n\n[   25.694973] BUG: kernel NULL pointer dereference, address: 0000000000000038\n[   25.695006] #PF: supervisor read access in kernel mode\n[   25.695012] #PF: error_code(0x0000) - not-present page\n[   25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0\n[   25.695025] Oops: Oops: 0000 [#1] SMP NOPTI\n[   25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt Not\ntainted 6.17.0-rc4 #1 PREEMPT(lazy)\n[   25.695040] Hardware name: VMware, Inc. VMware Virtual\nPlatform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020\n[   25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950\n[   25.695066] Code: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54\n24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b\n5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28\n85 c9\n[   25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203\n[   25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220\n[   25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180\n[   25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000\n[   25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7\n[   25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0\n[   25.695154] FS:  00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000)\nknlGS:0000000000000000\n[   25.695162] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0\n[   25.695201] Call Trace:\n[   25.695209]  <TASK>\n[   25.695215]  __x64_sys_fanotify_mark+0x1f/0x30\n[   25.695222]  do_syscall_64+0x82/0x2c0\n..."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfanotify: Validar el valor de retorno de mnt_ns_from_dentry() antes de desreferenciar\n\nLa función do_fanotify_mark() no valida si\nmnt_ns_from_dentry() devuelve NULL antes de desreferenciar mntns->user_ns.\nEsto causa una desreferencia de puntero NULL en do_fanotify_mark() si la\nruta no es un objeto de espacio de nombres de montaje.\n\nCorregir esto comprobando el valor de retorno de mnt_ns_from_dentry() antes de\ndesreferenciarlo.\n\nAntes del parche\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operación no permitida\n$ unshare -Urm\nFanotify fd: 3\nTerminado\n\nint main(void){\n    int ffd;\n    ffd = fanotify_init(FAN_CLASS_NOTIF | FAN_REPORT_MNT, 0);\n    if(ffd < 0){\n        perror(“fanotify_init”);\n        exit(EXIT_FAILURE);\n    }\n\n    printf(“Fanotify fd: %d\\n”,ffd);\n\n    if(fanotify_mark(ffd, FAN_MARK_ADD | FAN_MARK_MNTNS,\nFAN_MNT_ATTACH, AT_FDCWD, “A”) < 0){\n        perror(“fanotify_mark”);\n        exit(EXIT_FAILURE);\n    }\n\nreturn 0;\n}\n\nDespués del parche\n\n$ gcc fanotify_nullptr.c -o fanotify_nullptr\n$ mkdir A\n$ ./fanotify_nullptr\nFanotify fd: 3\nfanotify_mark: Operación no permitida\n$ unshare -Urm\nFanotify fd: 3\nfanotify_mark: Argumento inválido\n\n[   25.694973] BUG: desreferencia de puntero NULL del kernel, dirección: 0000000000000038\n[   25.695006] #PF: acceso de lectura de supervisor en modo kernel\n[   25.695012] #PF: error_code(0x0000) - página no presente\n[   25.695017] PGD 109a30067 P4D 109a30067 PUD 142b46067 PMD 0\n[   25.695025] Oops: Oops: 0000 [#1] SMP NOPTI\n[   25.695032] CPU: 4 UID: 1000 PID: 1478 Comm: fanotify_nullpt No\ncontaminado 6.17.0-rc4 #1 PREEMPT(lazy)\n[   25.695040] Nombre del hardware: VMware, Inc. VMware Virtual\nPlatform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020\n[   25.695049] RIP: 0010:do_fanotify_mark+0x817/0x950\n[   25.695066] Código: 04 00 00 e9 45 fd ff ff 48 8b 7c 24 48 4c 89 54\n24 18 4c 89 5c 24 10 4c 89 0c 24 e8 b3 11 fc ff 4c 8b 54 24 18 4c 8b\n5c 24 10 <48> 8b 78 38 4c 8b 0c 24 49 89 c4 e9 13 fd ff ff 8b 4c 24 28\n85 c9\n[   25.695081] RSP: 0018:ffffd31c469e3c08 EFLAGS: 00010203\n[   25.695104] RAX: 0000000000000000 RBX: 0000000001000000 RCX: ffff8eb48aebd220\n[   25.695110] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8eb4835e8180\n[   25.695115] RBP: 0000000000000111 R08: 0000000000000000 R09: 0000000000000000\n[   25.695142] R10: ffff8eb48a7d56c0 R11: ffff8eb482bede00 R12: 00000000004012a7\n[   25.695148] R13: 0000000000000110 R14: 0000000000000001 R15: ffff8eb48a7d56c0\n[   25.695154] FS:  00007f8733bda740(0000) GS:ffff8eb61ce5f000(0000)\nknlGS:0000000000000000\n[   25.695162] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n[   25.695170] CR2: 0000000000000038 CR3: 0000000136994006 CR4: 00000000003706f0\n[   25.695201] Traza de llamada:\n[   25.695209]  <TAREA>\n[   25.695215]  __x64_sys_fanotify_mark+0x1f/0x30\n[   25.695222]  do_syscall_64+0x82/0x2c0\n..."
    }
  ],
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "programFiles": [
            "fs/notify/fanotify/fanotify_user.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "58f5fbeb367ff6f30a2448b2cad70f70b2de4b06",
              "lessThan": "73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa",
              "versionType": "git",
              "status": "affected"
            },
            {
              "version": "58f5fbeb367ff6f30a2448b2cad70f70b2de4b06",
              "lessThan": "62e59ffe8787b5550ccff70c30b6f6be6a3ac3dd",
              "versionType": "git",
              "status": "affected"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "programFiles": [
            "fs/notify/fanotify/fanotify_user.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "versions": [
            {
              "version": "6.16",
              "status": "affected"
            },
            {
              "version": "0",
              "lessThan": "6.16",
              "versionType": "semver",
              "status": "unaffected"
            },
            {
              "version": "6.17.3",
              "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/62e59ffe8787b5550ccff70c30b6f6be6a3ac3dd",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/73ce2a774ad6497cbd48dc4f8a5d699bc417f3fa",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ]
}