{"cve":"CVE-2024-42305","nvd":{"published":"2024-08-17T09:15:10.690","modified":"2026-10-15T01:18:46.367","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-125"],"references":["https://git.kernel.org/stable/c/19e13b4d7f0303186fcc891aba8d0de7c8fdbda8","https://git.kernel.org/stable/c/42d420517072028fb0eb852c358056b7717ba5aa","https://git.kernel.org/stable/c/50ea741def587a64e08879ce6c6a30131f7111e7","https://git.kernel.org/stable/c/8afe06ed3be7a874b3cd82ef5f8959aca8d6429a","https://git.kernel.org/stable/c/9d241b7a39af192d1bb422714a458982c7cc67a2"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:54:16.205165117+00:00"},"epss":{"cve":"CVE-2024-42305","score":0.00226,"percentile":0.13222,"date":"2026-10-26"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}