{
  "cveId": "CVE-2024-40955",
  "url": "https://patchblox.com/security/cve/CVE-2024-40955",
  "summary": "CVE-2024-40955 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-40955, released July 12, 2024. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  ext4: fix slab-out-of-bounds in ext4_mb_find_goo...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists()  We can trigger a slab-out-of-bounds with the following commands:      mkfs.ext4 -F /dev/$disk 10G     mount /dev/$disk /tmp/test     echo 2147483647 \u003E /sys/fs/ext4/$disk/mb_group_prealloc     echo test \u003E /tmp/test/file \u0026\u0026 sync  ================================================================== BUG: KASAN: slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists\u002B0x8a/0x200 [ext4] Read of size 8 at addr ffff888121b9d0f0 by task kworker/u2:0/11 CPU: 0 PID: 11 Comm: kworker/u2:0 Tainted: GL 6.7.0-next-20240118 #521 Call Trace:  dump_stack_lvl\u002B0x2c/0x50  kasan_report\u002B0xb6/0xf0  ext4_mb_find_good_group_avg_frag_lists\u002B0x8a/0x200 [ext4]  ext4_mb_regular_allocator\u002B0x19e9/0x2370 [ext4]  ext4_mb_new_blocks\u002B0x88a/0x1370 [ext4]  ext4_ext_map_blocks\u002B0x14f7/0x2390 [ext4]  ext4_map_blocks\u002B0x569/0xea0 [ext4]  ext4_do_writepages\u002B0x10f6/0x1bc0 [ext4] [...] ==================================================================  The flow of issue triggering is as follows:  // Set s_mb_group_prealloc to 2147483647 via sysfs ext4_mb_new_blocks   ext4_mb_normalize_request     ext4_mb_normalize_group_request       ac-\u003Eac_g_ex.fe_len = EXT4_SB(sb)-\u003Es_mb_group_prealloc   ext4_mb_regular_allocator     ext4_mb_choose_next_group       ext4_mb_choose_next_group_best_avail         mb_avg_fragment_size_order           order = fls(len) - 2 = 29         ext4_mb_find_good_group_avg_frag_lists           frag_list = \u0026sbi-\u003Es_mb_avg_fragment_size[order]           if (list_empty(frag_list)) // Trigger SOOB!  At 4k block size, the length of the s_mb_avg_fragment_size list is 14, but an oversized s_mb_group_prealloc is set, causing slab-out-of-bounds to be triggered by an attempt to access an element at index 29.  Add a new attr_id attr_clusters_in_group with values in the range [0, sbi-\u003Es_clusters_per_group] and declare mb_group_prealloc as that type to fix the issue. In addition avoid returning an order from mb_avg_fragment_size_order() greater than MB_NUM_ORDERS(sb) and reduce some useless loops.",
  "published": "2024-07-12T13:15:17Z",
  "severity": "medium",
  "cvss": 5.5,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
  "epss": 0.00239,
  "epssPercentile": 0.15026,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.9.7-1",
      "fix": "DEBIAN-CVE-2024-40955",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2024-40955",
      "released": "2024-07-12T13:15:17Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "6.9.7-1",
      "fix": "DEBIAN-CVE-2024-40955",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2024-40955",
      "released": "2024-07-12T13:15:17Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T00:53:09Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}