[RFC][PATCH 2/5] lib: add error checking to hex2bin

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

hex2bin converts a hexadecimal string to its binary representation.
The original version of hex2bin did not do any error checking.  This
patch adds error checking and returns the result.

Changelog:
- use the new unpack_hex_byte()
- add __must_check compiler option (Andy Shevchenko's suggestion)
- change function API to return error checking result
  (based on Tetsuo Handa's initial patch)

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 include/linux/kernel.h |    2 +-
 lib/hexdump.c          |   11 +++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d8ea13b..3021e64 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -382,7 +382,7 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 }
 
 extern int hex_to_bin(char ch);
-extern void hex2bin(u8 *dst, const char *src, size_t count);
+extern bool __must_check hex2bin(u8 *dst, const char *src, size_t count);
 
 /*
  * unpack_hex_byte - convert 2 asii hex digits into a byte
diff --git a/lib/hexdump.c b/lib/hexdump.c
index f5fe6ba..7711095 100644
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -38,14 +38,17 @@ EXPORT_SYMBOL(hex_to_bin);
  * @dst: binary result
  * @src: ascii hexadecimal string
  * @count: result length
+ *
+ * Returns true on success, false in case of bad input.
  */
-void hex2bin(u8 *dst, const char *src, size_t count)
+bool hex2bin(u8 *dst, const char *src, size_t count)
 {
 	while (count--) {
-		*dst = hex_to_bin(*src++) << 4;
-		*dst += hex_to_bin(*src++);
-		dst++;
+		if (!unpack_hex_byte(dst++, src))
+			return false;
+		src += 2;
 	}
+	return true;
 }
 EXPORT_SYMBOL(hex2bin);
 
-- 
1.7.3.4