kernel/sysctl_binary.c: use generic UUID library

UUID library provides uuid_be type and uuid_be_to_bin() function.  This
substitutes open coded variant by generic library calls.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sysctl_binary.c

@@ -13,6 +13,7 @@
 #include <linux/ctype.h>
 #include <linux/netdevice.h>
 #include <linux/kernel.h>
+#include <linux/uuid.h>
 #include <linux/slab.h>
 #include <linux/compat.h>
 
@@ -1117,9 +1118,8 @@ static ssize_t bin_uuid(struct file *file,
 
 	/* Only supports reads */
 	if (oldval && oldlen) {
-		char buf[40], *str = buf;
-		unsigned char uuid[16];
-		int i;
+		char buf[UUID_STRING_LEN + 1];
+		uuid_be uuid;
 
 		result = kernel_read(file, 0, buf, sizeof(buf) - 1);
 		if (result < 0)
@@ -1127,24 +1127,15 @@ static ssize_t bin_uuid(struct file *file,
 
 		buf[result] = '\0';
 
-		/* Convert the uuid to from a string to binary */
-		for (i = 0; i < 16; i++) {
-			result = -EIO;
-			if (!isxdigit(str[0]) || !isxdigit(str[1]))
-				goto out;
-
-			uuid[i] = (hex_to_bin(str[0]) << 4) |
-					hex_to_bin(str[1]);
-			str += 2;
-			if (*str == '-')
-				str++;
-		}
+		result = -EIO;
+		if (uuid_be_to_bin(buf, &uuid))
+			goto out;
 
 		if (oldlen > 16)
 			oldlen = 16;
 
 		result = -EFAULT;
-		if (copy_to_user(oldval, uuid, oldlen))
+		if (copy_to_user(oldval, &uuid, oldlen))
 			goto out;
 
 		copied = oldlen;