Merge branch 'rs/apply-fuzzy-match-fix' into maint

A fix for an ancient bug in "git apply --ignore-space-change" codepath.

* rs/apply-fuzzy-match-fix:
  apply: avoid out-of-bounds access in fuzzy_matchlines()

1 files changed, 20 insertions, 39 deletions

diff --git a/apply.c b/apply.c
index c022af53a2..d4c1dd7efd 100644
--- a/apply.c
+++ b/apply.c
@@ -305,52 +305,33 @@ static uint32_t hash_line(const char *cp, size_t len)
 static int fuzzy_matchlines(const char *s1, size_t n1,
 			    const char *s2, size_t n2)
 {
-	const char *last1 = s1 + n1 - 1;
-	const char *last2 = s2 + n2 - 1;
-	int result = 0;
+	const char *end1 = s1 + n1;
+	const char *end2 = s2 + n2;
 
 	/* ignore line endings */
-	while ((*last1 == '\r') || (*last1 == '\n'))
-		last1--;
-	while ((*last2 == '\r') || (*last2 == '\n'))
-		last2--;
-
-	/* skip leading whitespaces, if both begin with whitespace */
-	if (s1 <= last1 && s2 <= last2 && isspace(*s1) && isspace(*s2)) {
-		while (isspace(*s1) && (s1 <= last1))
-			s1++;
-		while (isspace(*s2) && (s2 <= last2))
-			s2++;
-	}
-	/* early return if both lines are empty */
-	if ((s1 > last1) && (s2 > last2))
-		return 1;
-	while (!result) {
-		result = *s1++ - *s2++;
-		/*
-		 * Skip whitespace inside. We check for whitespace on
-		 * both buffers because we don't want "a b" to match
-		 * "ab"
-		 */
-		if (isspace(*s1) && isspace(*s2)) {
-			while (isspace(*s1) && s1 <= last1)
+	while (s1 < end1 && (end1[-1] == '\r' || end1[-1] == '\n'))
+		end1--;
+	while (s2 < end2 && (end2[-1] == '\r' || end2[-1] == '\n'))
+		end2--;
+
+	while (s1 < end1 && s2 < end2) {
+		if (isspace(*s1)) {
+			/*
+			 * Skip whitespace. We check on both buffers
+			 * because we don't want "a b" to match "ab".
+			 */
+			if (!isspace(*s2))
+				return 0;
+			while (s1 < end1 && isspace(*s1))
 				s1++;
-			while (isspace(*s2) && s2 <= last2)
+			while (s2 < end2 && isspace(*s2))
 				s2++;
-		}
-		/*
-		 * If we reached the end on one side only,
-		 * lines don't match
-		 */
-		if (
-		    ((s2 > last2) && (s1 <= last1)) ||
-		    ((s1 > last1) && (s2 <= last2)))
+		} else if (*s1++ != *s2++)
 			return 0;
-		if ((s1 > last1) && (s2 > last2))
-			break;
 	}
 
-	return !result;
+	/* If we reached the end on one side only, lines don't match. */
+	return s1 == end1 && s2 == end2;
 }
 
 static void add_line_info(struct image *img, const char *bol, size_t len, unsigned flag)