lib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users()

{
  "id": "98fbe0298bb2f3fee1d78dc4549e15fd4434fdde271495319cbc3a4dc5a2a47a",
  "url": "https://osv.dev/vulnerability/CVE-2025-38517",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "lib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: lib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users() alloc_tag_top_users() attempts to lock alloc_tag_cttype->mod_lock even when the alloc_tag_cttype is not allocated because: 1) alloc tagging is disabled because mem profiling is disabled (!alloc_tag_cttype) 2) alloc tagging is enabled, but not yet initialized (!alloc_tag_cttype) 3) alloc tagging is enabled, but failed initialization (!alloc_tag_cttype or IS_ERR(alloc_tag_cttype)) In all cases, alloc_tag_cttype is not allocated, and therefore alloc_tag_top_users() should not attempt to acquire the semaphore. This leads to a crash on memory allocation failure by attempting to acquire a non-existent semaphore: Oops: general protection fault, probably for non-canonical address 0xdffffc000000001b: 0000 [#3] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df] CPU: 2 UID: 0 PID: 1 Comm: systemd Tainted: G D 6.16.0-rc2 #1 VOLUNTARY Tainted: [D]=DIE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:down_read_trylock+0xaa/0x3b0 Code: d0 7c 08 84 d2 0f 85 a0 02 00 00 8b 0d df 31 dd 04 85 c9 75 29 48 b8 00 00 00 00 00 fc ff df 48 8d 6b 68 48 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 88 02 00 00 48 3b 5b 68 0f 85 53 01 00 00 65 ff RSP: 0000:ffff8881002ce9b8 EFLAGS: 00010016 RAX: dffffc0000000000 RBX: 0000000000000070 RCX: 0000000000000000 RDX: 000000000000001b RSI: 00",
    "evidence": "osv:CVE-2025-38517",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.39",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.15.7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-38517",
      "aliases": [
        "CVE-2025-38517"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "1438d349d16b78d88f9e978a4a5496f078c8191b"
                },
                {
                  "fixed": "febc0b5dbabda414565bdfaaaa59d26f787d5fe7"
                },
                {
                  "fixed": "22bf79c0c2301b6e15a688220284b147774d277e"
                },
                {
                  "fixed": "99af22cd34688cc0d535a1919e0bea4cbc6c1ea1"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38517.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.10.0"
                },
                {
                  "fixed": "6.12.39"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.15.7"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-38517.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:49.636739330Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/22bf79c0c2301b6e15a688220284b147774d277e",
        "https://git.kernel.org/stable/c/99af22cd34688cc0d535a1919e0bea4cbc6c1ea1",
        "https://git.kernel.org/stable/c/febc0b5dbabda414565bdfaaaa59d26f787d5fe7",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38517.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-38517",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/38xxx/CVE-2025-38517.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-38517",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 517742,
  "published_at": "2025-08-16T10:55:04.217+00:00"
}