staging: rtl8723bs: fix OOB write in HT_caps_handler()

Overview

In the Linux kernel, the following vulnerability has been resolved:

staging: rtl8723bs: fix OOB write in HT_caps_handler()

HT_caps_handler() iterates pIE->length bytes and writes into HT_caps.u.HT_cap[], which is a fixed 26-byte array (sizeof struct HT_caps_element). Because pIE->length is a raw u8 from an over-the-air 802.11 AssocResponse frame and is never validated, a malicious AP can set it up to 255, causing up to 229 bytes of out-of-bounds writes into adjacent fields of struct mlme_ext_info.

Truncate the iteration count to the size of HT_caps.u.HT_cap using umin() so that data from a longer-than-expected IE is silently ignored rather than written out of bounds, preserving interoperability with APs that pad the element. An early return on oversized IEs was considered but rejected: it would bypass the pmlmeinfo->HT_caps_enable = 1 assignment that precedes the loop, silently disabling HT mode for APs that append extra bytes to the HT Capabilities IE.

Affected

• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 37f642d47c3648a707df3ceb092eee1adffbfd28
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 8c872b47c7fc32e95e0da1db7512388794adcd69
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < bb3b942da4123b55d1cacf19d1a7d5ba15dbf83a
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 918537a0fbed85aab61fa28ad75e6279070610c9
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 6f91621fc45025ad3c0be796b70e6e4cee22fc69
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < 225b6d3fc7e99ac3d20b6c861d1e47d24e7ea31d
• Linux >= 554c0a3abf216c991c5ebddcdb2c08689ecd290b < f8001e1a516ba3b495728c65b61f799cbfad6bd0
• Linux 4.12

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.