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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < 45b06bb5ea96f75ad81d7ef446f832ea6b0026feaffected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < 426ef05e82ee52c8d0e95fc0808b7383d8352d73affected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < ddd57ebce245f9c7e2f6902a6c087d6186d2385daffected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < 755b40903eff563768d4d96fd4ef51ec48adde3baffected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < 5718df131ab78897a9dd1f2e71c3ba732d4392afaffected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < 277cedabb0ab86baae83fa58218be13c6d3e5526affected99d263d4c5b2f541dfacb5391e22e8c91ea982a6 to < f08fe8891c3eeb63b73f9f1f6d97aa629c821579affectedd4c96061fddd129778ce8b70fb093aa532f422d0affectedbe2378cbffe50ce0161f0fdee914adee98af53dcaffecteda8be8af18485f9fade90e1743d940252a39eec84affectedb5cf3193759f7cd1cfbeef11f5cf067bbce22e55affected3.10.55 to < 3.11affected3.12.29 to < 3.13affected3.14.19 to < 3.15affected3.16.3 to < 3.17affected
Linux Linux
Default version status: affected
3.17affected0 to < 3.17unaffected6.1.175 to ≤ 6.1.*unaffected6.6.136 to ≤ 6.6.*unaffected6.12.83 to ≤ 6.12.*unaffected6.18.24 to ≤ 6.18.*unaffected6.19.14 to ≤ 6.19.*unaffected7.0.1 to ≤ 7.0.*unaffected7.1 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/45b06bb5ea96f75ad81d7ef446f832ea6b0026fe ↗
- https://git.kernel.org/stable/c/426ef05e82ee52c8d0e95fc0808b7383d8352d73 ↗
- https://git.kernel.org/stable/c/ddd57ebce245f9c7e2f6902a6c087d6186d2385d ↗
- https://git.kernel.org/stable/c/755b40903eff563768d4d96fd4ef51ec48adde3b ↗
- https://git.kernel.org/stable/c/5718df131ab78897a9dd1f2e71c3ba732d4392af ↗
- https://git.kernel.org/stable/c/277cedabb0ab86baae83fa58218be13c6d3e5526 ↗
- https://git.kernel.org/stable/c/f08fe8891c3eeb63b73f9f1f6d97aa629c821579 ↗
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-784472.html ↗