From: Matthew Dobson <colpatch@us.ibm.com>

Commentary, choose better names for a few locals.


---

 lib/bitmap.c |   31 ++++++++++++++++++++++++-------
 1 files changed, 24 insertions(+), 7 deletions(-)

diff -puN lib/bitmap.c~bitmap-parsing-cleanup lib/bitmap.c
--- 25/lib/bitmap.c~bitmap-parsing-cleanup	2004-01-20 09:24:14.000000000 -0800
+++ 25-akpm/lib/bitmap.c	2004-01-20 09:24:14.000000000 -0800
@@ -210,13 +210,13 @@ EXPORT_SYMBOL(bitmap_snprintf);
  * bits of the resultant bitmask.  No chunk may specify a value larger
  * than 32 bits (-EOVERFLOW), and if a chunk specifies a smaller value
  * then leading 0-bits are prepended.  -EINVAL is returned for illegal
- * characters and for grouping errors such as "1,,5", ,44", "," and "".
+ * characters and for grouping errors such as "1,,5", ",44", "," and "".
  * Leading and trailing whitespace accepted, but not embedded whitespace.
  */
 int bitmap_parse(const char __user *ubuf, unsigned int ubuflen,
         unsigned long *maskp, int nmaskbits)
 {
-	int i, c, oc, ndigits, totaldigits, nchunks, nbits;
+	int i, c, old_c, totaldigits, ndigits, nchunks, nbits;
 	u32 chunk;
 
 	bitmap_clear(maskp, nmaskbits);
@@ -224,21 +224,39 @@ int bitmap_parse(const char __user *ubuf
 	nchunks = nbits = totaldigits = c = 0;
 	do {
 		chunk = ndigits = 0;
+
+		/* Get the next chunk of the bitmap */
 		while (ubuflen) {
-			oc = c;
+			old_c = c;
 			if (get_user(c, ubuf++))
 				return -EFAULT;
 			ubuflen--;
 			if (isspace(c))
 				continue;
-			if (totaldigits && c && isspace(oc))
+
+			/*
+			 * If the last character was a space and the current
+			 * character isn't '\0', we've got embedded whitespace.
+			 * This is a no-no, so throw an error.
+			 */
+			if (totaldigits && c && isspace(old_c))
 				return -EINVAL;
-			if (!c || c == ',')
+
+			/* A '\0' or a ',' signal the end of the chunk */
+			if (c == '\0' || c == ',')
 				break;
+
 			if (!isxdigit(c))
 				return -EINVAL;
+
+			/*
+			 * Make sure there are at least 4 free bits in 'chunk'.
+			 * If not, this hexdigit will overflow 'chunk', so
+			 * throw an error.
+			 */
 			if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
 				return -EOVERFLOW;
+
 			chunk = (chunk << 4) | unhex(c);
 			ndigits++; totaldigits++;
 		}
@@ -246,6 +264,7 @@ int bitmap_parse(const char __user *ubuf
 			return -EINVAL;
 		if (nchunks == 0 && chunk == 0)
 			continue;
+
 		bitmap_shift_right(maskp, maskp, CHUNKSZ, nmaskbits);
 		for (i = 0; i < CHUNKSZ; i++)
 			if (chunk & (1 << i))
@@ -256,8 +275,6 @@ int bitmap_parse(const char __user *ubuf
 			return -EOVERFLOW;
 	} while (ubuflen && c == ',');
 
-	if (totaldigits == 0)
-		return -EINVAL;
 	return 0;
 }
 EXPORT_SYMBOL(bitmap_parse);

_