Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: control: Validate buf_len before strnlen() in snd_ctl_elem_init_enum_names() snd_ctl_elem_init_enum_names() advances pointer p through the names buffer while decrementing buf_len. If buf_len reaches zero but items remain, the next iteration calls strnlen(p, 0). While strnlen(p, 0) returns 0 and would hit the existing name_len == 0 error path, CONFIG_FORTIFY_SOURCE's fortified strnlen() first checks maxlen against __builtin_dynamic_object_size(). When Clang loses track of p's object size inside the loop, this triggers a BRK exception panic before the return value is examined. Add a buf_len == 0 guard at the loop entry to prevent calling fortified strnlen() on an exhausted buffer. Found by kernel fuzz testing through Xiaomi Smartphone.

References 8

• git.kernel.org https://git.kernel.org/stable/c/1fbe46d2b72754d8bd580e13e59ccb5d3d0e8cb0
• git.kernel.org https://git.kernel.org/stable/c/654c818a69c21d2bea4e8fd9eae7da865df9a5c8
• git.kernel.org https://git.kernel.org/stable/c/708f6ec9bcdf58bfd561409110baaf4fd3be4ea3
• git.kernel.org https://git.kernel.org/stable/c/82012fd3e78a14360fbc2f1a7491589896704f97
• git.kernel.org https://git.kernel.org/stable/c/8ba0214c3dd32b8ec652947e3f2bc5b8f6e6be9e
• git.kernel.org https://git.kernel.org/stable/c/a470f7cabc4df72d9bd132f5719a8717292bb440
• git.kernel.org https://git.kernel.org/stable/c/bfcbb4994da9e979c4bcfcf24aaaac69e457e48e
• git.kernel.org https://git.kernel.org/stable/c/e0da8a8cac74f4b9f577979d131f0d2b88a84487

Remediation