CVE-2024-50301

Summary

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]):

  1. Obtain more than 32 inputs that have similar hashes, which ends with the pattern '0xxxxxxxe6'.
  2. Reboot and add the keys obtained in step 1.

The reproducer demonstrates how this issue happened:

  1. 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.

  2. 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.

  3. 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 | +—+

  4. 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/1cfa878e-8c7b-4570-8606-21daf5e13ce7@huaweicloud.com/

[jarkko: tweaked the commit message a bit to have an appropriate closes tag.]

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < c3ce634ad953ce48c75c39bdfd8b711dd95f346faffected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < 4efb69a0e294ef201bcdf7ce3d6202cd0a545a5daffected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < 1e4332581cd4eed75aea77af6f66cdcdda8b49b9affected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < 199c20fb7499c79557a075dc24e9a7dae7d9f1ceaffected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < bbad2d5b6c99db468d8f88b6ba6a56ed409b4881affected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < 3e79ad156bedf2da0ab909a118d2cec6c9c22b79affected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < e0a317ad68e4ea48a0158187238c5407e4fdec8baffected
LinuxLinuxb2a4df200d570b2c33a57e1ebfa5896e4bc81b69 < 4a74da044ec9ec8679e6beccc4306b936b62873faffected
LinuxLinux3.13affected
LinuxLinux0 < 3.13unaffected
LinuxLinux4.19.324 <= 4.19.*unaffected
LinuxLinux5.4.286 <= 5.4.*unaffected
LinuxLinux5.10.230 <= 5.10.*unaffected
LinuxLinux5.15.172 <= 5.15.*unaffected
LinuxLinux6.1.117 <= 6.1.*unaffected
LinuxLinux6.6.61 <= 6.6.*unaffected
LinuxLinux6.11.8 <= 6.11.*unaffected
LinuxLinux6.12 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

CVE Program Container

Additional References

Additional References

References