ssb: Fix range check in sprom write

The range check in the sprom image parser hex2sprom() is broken.
One sprom word is 4 hex characters.
This fixes the check and also adds much better sanity checks to the code.
We better make sure the image is OK by doing some sanity checks to avoid
bricking the device by accident.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/ssb/sprom.c

@@ -13,6 +13,8 @@
 
 #include "ssb_private.h"
 
+#include <linux/ctype.h>
+
 
 static const struct ssb_sprom *fallback_sprom;
 
@@ -33,17 +35,27 @@ static int sprom2hex(const u16 *sprom, char *buf, size_t buf_len,
 static int hex2sprom(u16 *sprom, const char *dump, size_t len,
 		     size_t sprom_size_words)
 {
-	char tmp[5] = { 0 };
-	int cnt = 0;
+	char c, tmp[5] = { 0 };
+	int err, cnt = 0;
 	unsigned long parsed;
 
-	if (len < sprom_size_words * 2)
+	/* Strip whitespace at the end. */
+	while (len) {
+		c = dump[len - 1];
+		if (!isspace(c) && c != '\0')
+			break;
+		len--;
+	}
+	/* Length must match exactly. */
+	if (len != sprom_size_words * 4)
 		return -EINVAL;
 
 	while (cnt < sprom_size_words) {
 		memcpy(tmp, dump, 4);
 		dump += 4;
-		parsed = simple_strtoul(tmp, NULL, 16);
+		err = strict_strtoul(tmp, 16, &parsed);
+		if (err)
+			return err;
 		sprom[cnt++] = swab16((u16)parsed);
 	}