GHSA-977X-CRV2-W57M
Vulnerability from github – Published: 2026-05-05 18:33 – Updated: 2026-09-08 09:35In the Linux kernel, the following vulnerability has been resolved:
dcache: Limit the minimal number of bucket to two
There is an OOB read problem on dentry_hashtable when user sets 'dhash_entries=1': BUG: unable to handle page fault for address: ffff888b30b774b0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP PTI RIP: 0010:__d_lookup+0x56/0x120 Call Trace: d_lookup.cold+0x16/0x5d lookup_dcache+0x27/0xf0 lookup_one_qstr_excl+0x2a/0x180 start_dirop+0x55/0xa0 simple_start_creating+0x8d/0xa0 debugfs_start_creating+0x8c/0x180 debugfs_create_dir+0x1d/0x1c0 pinctrl_init+0x6d/0x140 do_one_initcall+0x6d/0x3d0 kernel_init_freeable+0x39f/0x460 kernel_init+0x2a/0x260
There will be only one bucket in dentry_hashtable when dhash_entries is set as one, and d_hash_shift is calculated as 32 by dcache_init(). Then, following process will access more than one buckets(which memory region is not allocated) in dentry_hashtable: d_lookup b = d_hash(hash) dentry_hashtable + ((u32)hashlen >> d_hash_shift) // The C standard defines the behavior of right shift amounts // exceeding the bit width of the operand as undefined. The // result of '(u32)hashlen >> d_hash_shift' becomes 'hashlen', // so 'b' will point to an unallocated memory region. hlist_bl_for_each_entry_rcu(b) hlist_bl_first_rcu(head) h->first // read OOB!
Fix it by limiting the minimal number of dentry_hashtable bucket to two, so that 'd_hash_shift' won't exceeds the bit width of type u32.
{
"affected": [],
"aliases": [
"CVE-2026-43071"
],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-05-05T16:16:16Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ndcache: Limit the minimal number of bucket to two\n\nThere is an OOB read problem on dentry_hashtable when user sets\n\u0027dhash_entries=1\u0027:\n BUG: unable to handle page fault for address: ffff888b30b774b0\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n Oops: Oops: 0000 [#1] SMP PTI\n RIP: 0010:__d_lookup+0x56/0x120\n Call Trace:\n d_lookup.cold+0x16/0x5d\n lookup_dcache+0x27/0xf0\n lookup_one_qstr_excl+0x2a/0x180\n start_dirop+0x55/0xa0\n simple_start_creating+0x8d/0xa0\n debugfs_start_creating+0x8c/0x180\n debugfs_create_dir+0x1d/0x1c0\n pinctrl_init+0x6d/0x140\n do_one_initcall+0x6d/0x3d0\n kernel_init_freeable+0x39f/0x460\n kernel_init+0x2a/0x260\n\nThere will be only one bucket in dentry_hashtable when dhash_entries is\nset as one, and d_hash_shift is calculated as 32 by dcache_init(). Then,\nfollowing process will access more than one buckets(which memory region\nis not allocated) in dentry_hashtable:\n d_lookup\n b = d_hash(hash)\n dentry_hashtable + ((u32)hashlen \u003e\u003e d_hash_shift)\n // The C standard defines the behavior of right shift amounts\n // exceeding the bit width of the operand as undefined. The\n // result of \u0027(u32)hashlen \u003e\u003e d_hash_shift\u0027 becomes \u0027hashlen\u0027,\n // so \u0027b\u0027 will point to an unallocated memory region.\n hlist_bl_for_each_entry_rcu(b)\n hlist_bl_first_rcu(head)\n h-\u003efirst // read OOB!\n\nFix it by limiting the minimal number of dentry_hashtable bucket to two,\nso that \u0027d_hash_shift\u0027 won\u0027t exceeds the bit width of type u32.",
"id": "GHSA-977x-crv2-w57m",
"modified": "2026-09-08T09:35:28Z",
"published": "2026-05-05T18:33:25Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-43071"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/277cedabb0ab86baae83fa58218be13c6d3e5526"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/426ef05e82ee52c8d0e95fc0808b7383d8352d73"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/45b06bb5ea96f75ad81d7ef446f832ea6b0026fe"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5718df131ab78897a9dd1f2e71c3ba732d4392af"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/755b40903eff563768d4d96fd4ef51ec48adde3b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ddd57ebce245f9c7e2f6902a6c087d6186d2385d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f08fe8891c3eeb63b73f9f1f6d97aa629c821579"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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