staging: rtl8723bs: fix out-of-bounds read in rtw_get_ie() parser

staging: rtl8723bs: fix out-of-bounds read in rtw_get_ie() parser

The Information Element (IE) parser rtw_get_ie() trusted the length
byte of each IE without validating that the IE body (len bytes after
the 2-byte header) fits inside the remaining frame buffer. A malformed
frame can advertise an IE length larger than the available data, causing
the parser to increment its pointer beyond the buffer end. This results
in out-of-bounds reads or, depending on the pattern, an infinite loop.

Fix by validating that (offset + 2 + len) does not exceed the limit
before accepting the IE or advancing to the next element.

This prevents OOB reads and ensures the parser terminates safely on
malformed frames.

Signed-off-by: Navaneeth K <knavaneeth786@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>