{
  "schema_version": "1.4.0",
  "id": "GHSA-59wj-ff55-qrvj",
  "modified": "2025-09-11T18:35:52Z",
  "published": "2025-09-11T18:35:51Z",
  "aliases": [
    "CVE-2025-39758"
  ],
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages\n\nEver since commit c2ff29e99a76 (\"siw: Inline do_tcp_sendpages()\"),\nwe have been doing this:\n\nstatic int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,\n                             size_t size)\n[...]\n        /* Calculate the number of bytes we need to push, for this page\n         * specifically */\n        size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);\n        /* If we can't splice it, then copy it in, as normal */\n        if (!sendpage_ok(page[i]))\n                msg.msg_flags &= ~MSG_SPLICE_PAGES;\n        /* Set the bvec pointing to the page, with len $bytes */\n        bvec_set_page(&bvec, page[i], bytes, offset);\n        /* Set the iter to $size, aka the size of the whole sendpages (!!!) */\n        iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);\ntry_page_again:\n        lock_sock(sk);\n        /* Sendmsg with $size size (!!!) */\n        rv = tcp_sendmsg_locked(sk, &msg, size);\n\nThis means we've been sending oversized iov_iters and tcp_sendmsg calls\nfor a while. This has a been a benign bug because sendpage_ok() always\nreturned true. With the recent slab allocator changes being slowly\nintroduced into next (that disallow sendpage on large kmalloc\nallocations), we have recently hit out-of-bounds crashes, due to slight\ndifferences in iov_iter behavior between the MSG_SPLICE_PAGES and\n\"regular\" copy paths:\n\n(MSG_SPLICE_PAGES)\nskb_splice_from_iter\n  iov_iter_extract_pages\n    iov_iter_extract_bvec_pages\n      uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere\n  skb_splice_from_iter gets a \"short\" read\n\n(!MSG_SPLICE_PAGES)\nskb_copy_to_page_nocache copy=iov_iter_count\n [...]\n   copy_from_iter\n        /* this doesn't help */\n        if (unlikely(iter->count < len))\n                len = iter->count;\n          iterate_bvec\n            ... and we run off the bvecs\n\nFix this by properly setting the iov_iter's byte count, plus sending the\ncorrect byte count to tcp_sendmsg_locked.",
  "severity": [],
  "affected": [],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39758"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/42ebc16d9d2563f1a1ce0f05b643ee68d54fabf8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5661fdd218c2799001b88c17acd19f4395e4488e"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/673cf582fd788af12cdacfb62a6a593083542481"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c18646248fed07683d4cee8a8af933fc4fe83c0d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/edf82bc8150570167a33a7d54627d66614cbf841"
    }
  ],
  "database_specific": {
    "cwe_ids": [],
    "severity": null,
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-11T17:15:39Z"
  }
}