smb: client: fix crypto buffers in non-linear memory

{
  "id": "e82a3548a4b7236d1d71cc9c828ebef423a0f6e9cfaa8d779921e21f7d11169f",
  "url": "https://osv.dev/vulnerability/CVE-2025-40052",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "smb: client: fix crypto buffers in non-linear memory",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: smb: client: fix crypto buffers in non-linear memory The crypto API, through the scatterlist API, expects input buffers to be in linear memory. We handle this with the cifs_sg_set_buf() helper that converts vmalloc'd memory to their corresponding pages. However, when we allocate our aead_request buffer (@creq in smb2ops.c::crypt_message()), we do so with kvzalloc(), which possibly puts aead_request->__ctx in vmalloc area. AEAD algorithm then uses ->__ctx for its private/internal data and operations, and uses sg_set_buf() for such data on a few places. This works fine as long as @creq falls into kmalloc zone (small requests) or vmalloc'd memory is still within linear range. Tasks' stacks are vmalloc'd by default (CONFIG_VMAP_STACK=y), so too many tasks will increment the base stacks' addresses to a point where virt_addr_valid(buf) will fail (BUG() in sg_set_buf()) when that happens. In practice: too many parallel reads and writes on an encrypted mount will trigger this bug. To fix this, always alloc @creq with kmalloc() instead. Also drop the @sensitive_size variable/arguments since kfree_sensitive() doesn't need it. Backtrace: [ 945.272081] ------------[ cut here ]------------ [ 945.272774] kernel BUG at include/linux/scatterlist.h:209! [ 945.273520] Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI [ 945.274412] CPU: 7 UID: 0 PID: 56 Comm: kworker/u33:0 Kdump: loaded Not tainted 6.15.0-lku-11779-g8e9",
    "evidence": "osv:CVE-2025-40052",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "value": "6.6.112",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.12.53",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.17.3",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-40052",
      "aliases": [
        "CVE-2025-40052"
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      "affected": [
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                  "fixed": "4a61b68abd2788db0364c9a0b6a39f1699fea440"
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                {
                  "fixed": "998a67b954680f26f3734040aeeed08642d49721"
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          "package": {
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            "ecosystem": "Linux"
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          "database_specific": {
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      ],
      "modified": "2026-10-28T02:30:21.920970775Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4a61b68abd2788db0364c9a0b6a39f1699fea440",
        "https://git.kernel.org/stable/c/7a8a8c15468f0c99685e9964451feffd1a3cc859",
        "https://git.kernel.org/stable/c/998a67b954680f26f3734040aeeed08642d49721",
        "https://git.kernel.org/stable/c/ba905a567105dde21cdb8e6d3a87110fa434b393",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/40xxx/CVE-2025-40052.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-40052",
        "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/2025/40xxx/CVE-2025-40052.json"
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    "related_cves": [
      {
        "value": "CVE-2025-40052",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
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  "source_id": "core-osv",
  "document_id": 488302,
  "published_at": "2025-10-28T11:48:27.854+00:00"
}