{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2024-42305",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2024-42305"
  ],
  "published": "2024-08-17T09:11:20Z",
  "summary": "ext4: check dot and dotdot of dx_root before making dir indexed",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: check dot and dotdot of dx_root before making dir indexed\n\nSyzbot reports a issue as follows:\n============================================\nBUG: unable to handle page fault for address: ffffed11022e24fe\nPGD 23ffee067 P4D 23ffee067 PUD 0\nOops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI\nCPU: 0 PID: 5079 Comm: syz-executor306 Not tainted 6.10.0-rc5-g55027e689933 #0\nCall Trace:\n <TASK>\n make_indexed_dir+0xdaf/0x13c0 fs/ext4/namei.c:2341\n ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2451\n ext4_rename fs/ext4/namei.c:3936 [inline]\n ext4_rename2+0x26e5/0x4370 fs/ext4/namei.c:4214\n[...]\n============================================\n\nThe immediate cause of this problem is that there is only one valid dentry\nfor the block to be split during do_split, so split==0 results in out of\nbounds accesses to the map triggering the issue.\n\n    do_split\n      unsigned split\n      dx_make_map\n       count = 1\n      split = count/2 = 0;\n      continued = hash2 == map[split - 1].hash;\n       ---> map[4294967295]\n\nThe maximum length of a filename is 255 and the minimum block size is 1024,\nso it is always guaranteed that the number of entries is greater than or\nequal to 2 when do_split() is called.\n\nBut syzbot's crafted image has no dot and dotdot in dir, and the dentry\ndistribution in dirblock is as follows:\n\n  bus     dentry1          hole           dentry2           free\n|xx--|xx-------------|...............|xx-------------|...............|\n0   12 (8+248)=256  268     256     524 (8+256)=264 788     236     1024\n\nSo when renaming dentry1 increases its name_len length by 1, neither hole\nnor free is sufficient to hold the new dentry, and make_indexed_dir() is\ncalled.\n\nIn make_indexed_dir() it is assumed that the first two entries of the\ndirblock must be dot and dotdot, so bus and dentry1 are left in dx_root\nbecause they are treated as dot and dotdot, and only dentry2 is moved\nto the new leaf block. That's why count is equal to 1.\n\nTherefore add the ext4_check_dx_root() helper function to add more sanity\nchecks to dot and dotdot before starting the conversion to avoid the above\nissue.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
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        "1:6.1.47-1+rpt4",
        "1:6.1.54-1+rpt2",
        "1:6.1.58-1+rpt2",
        "1:6.1.63-1+rpt1",
        "1:6.1.73-1+rpt1",
        "1:6.6.20-1+rpt1",
        "1:6.6.28-1+rpt1",
        "1:6.6.31-1+rpt1"
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    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2024-42305"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b80575ffa98b5bb3a5d4d392bfe4c2e03e9557db"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/19e13b4d7f0303186fcc891aba8d0de7c8fdbda8"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/42d420517072028fb0eb852c358056b7717ba5aa"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/8afe06ed3be7a874b3cd82ef5f8959aca8d6429a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/abb411ac991810c0bcbe51c2e76d2502bf611b5c"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/9d241b7a39af192d1bb422714a458982c7cc67a2"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/cdd345321699042ece4a9d2e70754d2397d378c5"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/50ea741def587a64e08879ce6c6a30131f7111e7"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
  }
}