GHSA-M43V-97RG-MVC9

Vulnerability from github – Published: 2026-10-26 15:34 – Updated: 2026-10-26 15:34
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

riscv: patch: fix handling of bpf-jit execmem addresses

Commit 8718e5a3090b ("riscv: patch: skip fixmap mapping when kernel text is already writable") gated the core_kernel_text() branch of patch_map() on CONFIG_STRICT_KERNEL_RWX, and explicitly left the vmalloc branch unchanged. That branch has a separate problem.

That branch only creates a temporary writable fixmap alias when CONFIG_STRICT_MODULE_RWX is enabled, and otherwise assumes the target is directly writable and returns the address unchanged. That assumption no longer holds: bpf_prog_pack_alloc calls set_memory_rox() on every pack unconditionally in alloc_new_pack(), independently of any CONFIG_STRICT_*_RWX option, so BPF text in the vmalloc area is read-only regardless of what CONFIG_STRICT_MODULE_RWX says.

With CONFIG_STRICT_MODULE_RWX=n, patch_map() returns the read-only address directly, the subsequent copy_to_kernel_nofault() takes a page fault and returns -EFAULT. bpf_arch_text_copy() turns that into -EINVAL, which propagates through bpf_jit_binary_pack_finalize() to the WARN_ON() in bpf_int_jit_compile() and leaves the program un-JITed.

Note that BPF cannot be fixed the way kprobes was in commit bdc46e507b59 ("riscv: mm: make EXECMEM_KPROBES writable without CONFIG_STRICT_MODULE_RWX"). EXECMEM_BPF is already PAGE_KERNEL, i.e. writable at allocation time; the read-only mapping is established afterwards by generic code in alloc_new_pack(), which arch code cannot influence. The only place this can be handled is patch_map().

This is the same problem that was fixed on arm64 by commit b1480ed230ac ("arm64: patching: fix handling of execmem addresses"), and the fix is the same: CONFIG_EXECMEM is what actually tracks whether the vmalloc area can hold executable memory that needs a temporary alias to be written. CONFIG_BPF_JIT, CONFIG_KPROBES and CONFIG_MODULES all select it.

Note that this is not limited to CONFIG_MODULES=n. Unlike arm64, riscv selects CONFIG_ARCH_OPTIONAL_KERNEL_RWX, so CONFIG_STRICT_MODULE_RWX can be disabled with CONFIG_MODULES=y as well, and the bug is reachable in that configuration too.

The !CONFIG_MMU build is unaffected: it has its own __patch_insn_set() and __patch_insn_write() implementations and never calls patch_map().

Show details on source website

{
  "affected": [],
  "aliases": [
    "CVE-2026-99092"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-26T15:16:48Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: patch: fix handling of bpf-jit execmem addresses\n\nCommit 8718e5a3090b (\"riscv: patch: skip fixmap mapping when kernel text\nis already writable\") gated the core_kernel_text() branch of patch_map()\non CONFIG_STRICT_KERNEL_RWX, and explicitly left the vmalloc branch\nunchanged. That branch has a separate problem.\n\nThat branch only creates a temporary writable fixmap alias when\nCONFIG_STRICT_MODULE_RWX is enabled, and otherwise assumes the target is\ndirectly writable and returns the address unchanged. That assumption no\nlonger holds: bpf_prog_pack_alloc calls set_memory_rox() on every pack\nunconditionally in alloc_new_pack(), independently of any\nCONFIG_STRICT_*_RWX option, so BPF text in the vmalloc area is read-only\nregardless of what CONFIG_STRICT_MODULE_RWX says.\n\nWith CONFIG_STRICT_MODULE_RWX=n, patch_map() returns the read-only\naddress directly, the subsequent copy_to_kernel_nofault() takes a\npage fault and returns -EFAULT. bpf_arch_text_copy() turns that into\n-EINVAL, which propagates through bpf_jit_binary_pack_finalize() to the\nWARN_ON() in bpf_int_jit_compile() and leaves the program un-JITed.\n\nNote that BPF cannot be fixed the way kprobes was in\ncommit bdc46e507b59 (\"riscv: mm: make EXECMEM_KPROBES writable without\nCONFIG_STRICT_MODULE_RWX\"). EXECMEM_BPF is already PAGE_KERNEL, i.e.\nwritable at allocation time; the read-only mapping is established\nafterwards by generic code in alloc_new_pack(), which arch code cannot\ninfluence. The only place this can be handled is patch_map().\n\nThis is the same problem that was fixed on arm64 by commit b1480ed230ac\n(\"arm64: patching: fix handling of execmem addresses\"), and the fix is\nthe same: CONFIG_EXECMEM is what actually tracks whether the vmalloc\narea can hold executable memory that needs a temporary alias to be\nwritten. CONFIG_BPF_JIT, CONFIG_KPROBES and CONFIG_MODULES all select\nit.\n\nNote that this is not limited to CONFIG_MODULES=n. Unlike arm64, riscv\nselects CONFIG_ARCH_OPTIONAL_KERNEL_RWX, so CONFIG_STRICT_MODULE_RWX can\nbe disabled with CONFIG_MODULES=y as well, and the bug is reachable in\nthat configuration too.\n\nThe !CONFIG_MMU build is unaffected: it has its own __patch_insn_set()\nand __patch_insn_write() implementations and never calls patch_map().",
  "id": "GHSA-m43v-97rg-mvc9",
  "modified": "2026-10-26T15:34:50Z",
  "published": "2026-10-26T15:34:50Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99092"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/562a35b9e0b3d9483d9472995219cadb3592db3d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9e8fc7972b398e9dc2415ece283d8f64edac3858"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a510e1ae8c9030750c2edf7b0bc9b186cd8c7a06"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f71d6ea3843c8038c431c2699482f246aea37ca0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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