1 files changed, 49 insertions, 5 deletions

diff --git a/lib/libc/stdlib/realpath.c b/lib/libc/stdlib/realpath.c
index 3082f5f4b95a..31c93e677418 100644
--- a/lib/libc/stdlib/realpath.c
+++ b/lib/libc/stdlib/realpath.c
@@ -43,23 +43,37 @@ __FBSDID("$FreeBSD$");
 #include "un-namespace.h"
 
 /*
- * char *realpath(const char *path, char resolved[PATH_MAX]);
- *
  * Find the real name of path, by removing all ".", ".." and symlink
  * components.  Returns (resolved) on success, or (NULL) on failure,
  * in which case the path which caused trouble is left in (resolved).
  */
 char *
-realpath(const char *path, char resolved[PATH_MAX])
+realpath(const char * __restrict path, char * __restrict resolved)
 {
 	struct stat sb;
 	char *p, *q, *s;
 	size_t left_len, resolved_len;
 	unsigned symlinks;
-	int serrno, slen;
+	int serrno, slen, m;
 	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
 
+	if (path == NULL) {
+		errno = EINVAL;
+		return (NULL);
+	}
+	if (path[0] == '\0') {
+		errno = ENOENT;
+		return (NULL);
+	}
 	serrno = errno;
+	if (resolved == NULL) {
+		resolved = malloc(PATH_MAX);
+		if (resolved == NULL)
+			return (NULL);
+		m = 1;
+	} else
+		m = 0;
+
 	symlinks = 0;
 	if (path[0] == '/') {
 		resolved[0] = '/';
@@ -71,12 +85,19 @@ realpath(const char *path, char resolved[PATH_MAX])
 	} else {
 		if (getcwd(resolved, PATH_MAX) == NULL) {
 			strlcpy(resolved, ".", PATH_MAX);
+			if (m) {
+				serrno = errno;
+				free(resolved);
+				errno = serrno;
+			}
 			return (NULL);
 		}
 		resolved_len = strlen(resolved);
 		left_len = strlcpy(left, path, sizeof(left));
 	}
 	if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) {
+		if (m)
+			free(resolved);
 		errno = ENAMETOOLONG;
 		return (NULL);
 	}
@@ -92,6 +113,8 @@ realpath(const char *path, char resolved[PATH_MAX])
 		p = strchr(left, '/');
 		s = p ? p : left + left_len;
 		if (s - left >= sizeof(next_token)) {
+			if (m)
+				free(resolved);
 			errno = ENAMETOOLONG;
 			return (NULL);
 		}
@@ -102,6 +125,8 @@ realpath(const char *path, char resolved[PATH_MAX])
 			memmove(left, s + 1, left_len + 1);
 		if (resolved[resolved_len - 1] != '/') {
 			if (resolved_len + 1 >= PATH_MAX) {
+				if (m)
+					free(resolved);
 				errno = ENAMETOOLONG;
 				return (NULL);
 			}
@@ -133,6 +158,8 @@ realpath(const char *path, char resolved[PATH_MAX])
 		 */
 		resolved_len = strlcat(resolved, next_token, PATH_MAX);
 		if (resolved_len >= PATH_MAX) {
+			if (m)
+				free(resolved);
 			errno = ENAMETOOLONG;
 			return (NULL);
 		}
@@ -141,16 +168,29 @@ realpath(const char *path, char resolved[PATH_MAX])
 				errno = serrno;
 				return (resolved);
 			}
+			if (m) {
+				serrno = errno;
+				free(resolved);
+				errno = serrno;
+			}
 			return (NULL);
 		}
 		if (S_ISLNK(sb.st_mode)) {
 			if (symlinks++ > MAXSYMLINKS) {
+				if (m)
+					free(resolved);
 				errno = ELOOP;
 				return (NULL);
 			}
 			slen = readlink(resolved, symlink, sizeof(symlink) - 1);
-			if (slen < 0)
+			if (slen < 0) {
+				if (m) {
+					serrno = errno;
+					free(resolved);
+					errno = serrno;
+				}
 				return (NULL);
+			}
 			symlink[slen] = '\0';
 			if (symlink[0] == '/') {
 				resolved[1] = 0;
@@ -171,6 +211,8 @@ realpath(const char *path, char resolved[PATH_MAX])
 			if (p != NULL) {
 				if (symlink[slen - 1] != '/') {
 					if (slen + 1 >= sizeof(symlink)) {
+						if (m)
+							free(resolved);
 						errno = ENAMETOOLONG;
 						return (NULL);
 					}
@@ -179,6 +221,8 @@ realpath(const char *path, char resolved[PATH_MAX])
 				}
 				left_len = strlcat(symlink, left, sizeof(left));
 				if (left_len >= sizeof(left)) {
+					if (m)
+						free(resolved);
 					errno = ENAMETOOLONG;
 					return (NULL);
 				}