CVE-2026-43071
Description
In 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.
How to fix
- linux linux_kernel3.11, 3.13, 3.15, 3.17, 6.1.175, 6.6.136, 6.12.83, 6.18.24, 6.19.14, 7.0.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| linux linux_kernel | 3.10.55 ≤ v < 3.11, 3.12.29 ≤ v < 3.13, 3.14.19 ≤ v < 3.15, 3.16.3 ≤ v < 3.17, 3.17.1 ≤ v < 6.1.175, 6.2 ≤ v < 6.6.136, 6.7 ≤ v < 6.12.83, 6.13 ≤ v < 6.18.24, 6.19 ≤ v < 6.19.14, 7.0 ≤ v < 7.0.1, 3.17 | 3.11, 3.13, 3.15, 3.17, 6.1.175, 6.6.136, 6.12.83, 6.18.24, 6.19.14, 7.0.1 |
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