CVE-2024-50301High· 7.8▾ TwilightIn the Linux kernel, the following vulnerability has been resolved: security/keys: fix slab-out-of-bounds in key_task_permission KASAN reports an out of bounds read: BUG: KASAN: slab-out-of-bounds in __kuid_val include/linux/uidgid.h:3…
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 42.9 · likelihood 0.1 · exploitation 0
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Stakeholder-Specific Vulnerability Categorization from CISA's ADP record at CVE.org: whether exploitation is observed, whether an attack can be automated, and how much of the system is at stake.
Exploit-prediction probability, daily snapshots since Oct 15.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
Last analysed / modified upstream
0.3%
In the Linux kernel, the following vulnerability has been resolved:
security/keys: fix slab-out-of-bounds in key_task_permission
KASAN reports an out of bounds read: BUG: KASAN: slab-out-of-bounds in __kuid_val include/linux/uidgid.h:36 BUG: KASAN: slab-out-of-bounds in uid_eq include/linux/uidgid.h:63 [inline] BUG: KASAN: slab-out-of-bounds in key_task_permission+0x394/0x410 security/keys/permission.c:54 Read of size 4 at addr ffff88813c3ab618 by task stress-ng/4362
CPU: 2 PID: 4362 Comm: stress-ng Not tainted 5.10.0-14930-gafbffd6c3ede #15 Call Trace: __dump_stack lib/dump_stack.c:82 [inline] dump_stack+0x107/0x167 lib/dump_stack.c:123 print_address_description.constprop.0+0x19/0x170 mm/kasan/report.c:400 __kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560 kasan_report+0x3a/0x50 mm/kasan/report.c:585 __kuid_val include/linux/uidgid.h:36 [inline] uid_eq include/linux/uidgid.h:63 [inline] key_task_permission+0x394/0x410 security/keys/permission.c:54 search_nested_keyrings+0x90e/0xe90 security/keys/keyring.c:793
This issue was also reported by syzbot.
It can be reproduced by following these steps(more details [1]):
The reproducer demonstrates how this issue happened:
In the search_nested_keyrings function, when it iterates through the slots in a node(below tag ascend_to_node), if the slot pointer is meta and node->back_pointer != NULL(it means a root), it will proceed to descend_to_node. However, there is an exception. If node is the root, and one of the slots points to a shortcut, it will be treated as a keyring.
Whether the ptr is keyring decided by keyring_ptr_is_keyring function. However, KEYRING_PTR_SUBTYPE is 0x2UL, the same as ASSOC_ARRAY_PTR_SUBTYPE_MASK.
When 32 keys with the similar hashes are added to the tree, the ROOT has keys with hashes that are not similar (e.g. slot 0) and it splits NODE A without using a shortcut. When NODE A is filled with keys that all hashes are xxe6, the keys are similar, NODE A will split with a shortcut. Finally, it forms the tree as shown below, where slot 6 points to a shortcut.
NODE A
+------>+---+
ROOT | | 0 | xxe6 +---+ | +---+ xxxx | 0 | shortcut : : xxe6 +---+ | +---+ xxe6 : : | | | xxe6 +---+ | +---+ | 6 |---+ : : xxe6 +---+ +---+ xxe6 : : | f | xxe6 +---+ +---+ xxe6 | f | +---+
As mentioned above, If a slot(slot 6) of the root points to a shortcut, it may be mistakenly transferred to a key*, leading to a read out-of-bounds read.
To fix this issue, one should jump to descend_to_node if the ptr is a shortcut, regardless of whether the node is root or not.
[1] https://lore.kernel.org/linux-kernel/[email protected]/
[jarkko: tweaked the commit message a bit to have an appropriate closes tag.]
linux_kernel >= 3.13, < 4.19.324linux_kernel >= 4.20, < 5.4.286linux_kernel >= 5.5, < 5.10.230linux_kernel >= 5.11, < 5.15.172linux_kernel >= 5.16, < 6.1.117linux_kernel >= 6.2, < 6.6.61linux_kernel >= 6.7, < 6.11.8linux_kernel = 6.12Upgrade past the affected range:
linux_kernel 6.11.8Connected by shared product, vendor, weakness, or advisory.
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