ihex: Check if zero-length record is at the end of the blob

When verifying the validity of IHEX file we need to make sure that
zero-length record we found is located at the end of the file. Not
doing that could result in an invalid file with a bogus zero-length in
the middle short-circuiting the check and being reported as valid.

Cc: Chris Healy <cphealy@gmail.com>
Cc: Kyle McMartin <kyle@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/ihex.h

@@ -49,7 +49,7 @@ static inline int ihex_validate_fw(const struct firmware *fw)
 
 	for (; rec <= end; rec = __ihex_next_binrec(rec)) {
 		/* Zero length marks end of records */
-		if (!be16_to_cpu(rec->len))
+		if (rec == end && !be16_to_cpu(rec->len))
 			return 0;
 	}
 	return -EINVAL;