{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-31702",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2026-31702"
  ],
  "published": "2026-05-01T13:56:32Z",
  "summary": "f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()\n\nIn f2fs_compress_write_end_io(), dec_page_count(sbi, type) can bring\nthe F2FS_WB_CP_DATA counter to zero, unblocking\nf2fs_wait_on_all_pages() in f2fs_put_super() on a concurrent unmount\nCPU. The unmount path then proceeds to call\nf2fs_destroy_page_array_cache(sbi), which destroys\nsbi->page_array_slab via kmem_cache_destroy(), and eventually\nkfree(sbi). Meanwhile, the bio completion callback is still executing:\nwhen it reaches page_array_free(sbi, ...), it dereferences\nsbi->page_array_slab \u2014 a destroyed slab cache \u2014 to call\nkmem_cache_free(), causing a use-after-free.\n\nThis is the same class of bug as CVE-2026-23234 (which fixed the\nequivalent race in f2fs_write_end_io() in data.c), but in the\ncompressed writeback completion path that was not covered by that fix.\n\nFix this by moving dec_page_count() to after page_array_free(), so\nthat all sbi accesses complete before the counter decrement that can\nunblock unmount. For non-last folios (where atomic_dec_return on\ncic->pending_pages is nonzero), dec_page_count is called immediately\nbefore returning \u2014 page_array_free is not reached on this path, so\nthere is no post-decrement sbi access. For the last folio,\npage_array_free runs while the F2FS_WB_CP_DATA counter is still\nnonzero (this folio has not yet decremented it), keeping sbi alive,\nand dec_page_count runs as the final operation.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.175",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-31702"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/57bc678f36ac03281e877c6b84877b43f964143f"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ef57cd3329b40c739b9a2e1a8a21ecc4171c6280"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f5154cf3ce1c8193f0c1891d3769f62740cfe6fe"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/c76cf339b87975ae5b2c06d2d774d5667d25a12a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/2c97dcb6147c8f7f25c629b93be1e69617de5d4a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/39d4ee19c1e7d753dd655aebee632271b171f43a"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-06-15T02:03:26Z"
  }
}