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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
| Attack Vector | NETWORK |
|---|---|
| Attack Complexity | LOW |
| Privileges Required | NONE |
| User Interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality Impact | HIGH |
| Integrity Impact | NONE |
| Availability Impact | HIGH |
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Type: Secondary
Exploitability Score: 3.9
Impact Score: 5.2
| Source | Type | Description |
|---|---|---|
| [email protected] | Primary |
en
CWE-125
|
| Vendor | Product | Version | Update | Type |
|---|---|---|---|---|
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a5907800> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d235740a7c0> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a5906480> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d235740b000> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d235740b380> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d242a8c8b40> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a5907400> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23beb86800> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d239fbdc980> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23af2d23c0> | Operating System |
| linux | linux_kernel | 3.17 | <built-in method update of dict object at 0x7d23a53100c0> | Operating System |
| linux | linux_kernel | 3.17 | <built-in method update of dict object at 0x7d239fb7d8c0> | Operating System |
| linux | linux_kernel | 3.17 | <built-in method update of dict object at 0x7d239fb7f440> | Operating System |
| linux | linux_kernel | 3.17 | <built-in method update of dict object at 0x7d23beb6ba00> | Operating System |
| Vulnerable | CPE |
|---|---|
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:3.17:-:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:3.17:rc5:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:3.17:rc6:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:3.17:rc7:*:*:*:*:*:* |