CVE-2026-74651: staging: rtl8723bs: fix OOB read in rtw_get_wpa_ie()

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

staging: rtl8723bs: fix OOB read in rtwgetwpaie()

rtwgetwpaie() reads bytes at fixed offsets into a vendor-specific information element without checking that the element is long enough, causing an out-of-bounds read for a short trailing IE.

The function locates a vendor-specific IE (EID 221) with rtwgetie() and then compares a 4-byte OUI+type at pbuf + 2 and reads a 2-byte version word at pbuf + 6. Those accesses require the IE body to be at least 6 bytes, but rtwgetie() only guarantees that the element fits within the buffer; it does not enforce a minimum body length. A vendor-specific IE whose length byte is 0 to 5, placed at the end of the buffer, therefore makes these reads run past the end of the IE and past the end of the buffer itself.

The buffer holds information elements taken from received management frames and from the IE blob passed to rtwcfg80211setwpaie(), which is kmemdup'd to its exact length, so the read can run off the end of the allocation.

The sibling helpers rtwgetsecie(), rtwgetwapiie() and rtwgetwpsie() in this file already reject too-short vendor-specific IEs before their OUI memcmp(); rtwgetwpaie() was never brought in line with them, and needs a minimum of 6 rather than 4 bytes because of the version word. Add the missing length check.