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Date:      Mon, 15 May 2017 17:34:17 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r318299 - head/lib/libc/stdlib
Message-ID:  <201705151734.v4FHYHPv035245@repo.freebsd.org>
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Author: kib
Date: Mon May 15 17:34:17 2017
New Revision: 318299
URL: https://svnweb.freebsd.org/changeset/base/318299

Log:
  Simplify cleanup on failure in realpath(3).
  
  If realpath() allocated memory for result and failed, the memory is
  freed in each place where return is performed.  More, the function
  needs to track the allocation status, to not free user-supplied
  buffer.
  
  Consolidate the memory handling in the wrapper, freeing the buffer if
  the actual worker failed.
  
  Reviewed by:	emaste (previous version)
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks
  Differential revision:	https://reviews.freebsd.org/D10670

Modified:
  head/lib/libc/stdlib/realpath.c

Modified: head/lib/libc/stdlib/realpath.c
==============================================================================
--- head/lib/libc/stdlib/realpath.c	Mon May 15 17:14:53 2017	(r318298)
+++ head/lib/libc/stdlib/realpath.c	Mon May 15 17:34:17 2017	(r318299)
@@ -47,32 +47,16 @@ __FBSDID("$FreeBSD$");
  * 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 * __restrict path, char * __restrict resolved)
+static char *
+realpath1(const char *path, char *resolved)
 {
 	struct stat sb;
 	char *p, *q;
 	size_t left_len, resolved_len, next_token_len;
 	unsigned symlinks;
-	int m;
 	ssize_t slen;
 	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);
-	}
-	if (resolved == NULL) {
-		resolved = malloc(PATH_MAX);
-		if (resolved == NULL)
-			return (NULL);
-		m = 1;
-	} else
-		m = 0;
 	symlinks = 0;
 	if (path[0] == '/') {
 		resolved[0] = '/';
@@ -83,20 +67,14 @@ realpath(const char * __restrict path, c
 		left_len = strlcpy(left, path + 1, sizeof(left));
 	} else {
 		if (getcwd(resolved, PATH_MAX) == NULL) {
-			if (m)
-				free(resolved);
-			else {
-				resolved[0] = '.';
-				resolved[1] = '\0';
-			}
+			resolved[0] = '.';
+			resolved[1] = '\0';
 			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);
 	}
@@ -125,8 +103,6 @@ realpath(const char * __restrict path, c
 
 		if (resolved[resolved_len - 1] != '/') {
 			if (resolved_len + 1 >= PATH_MAX) {
-				if (m)
-					free(resolved);
 				errno = ENAMETOOLONG;
 				return (NULL);
 			}
@@ -158,27 +134,18 @@ realpath(const char * __restrict path, c
 		 */
 		resolved_len = strlcat(resolved, next_token, PATH_MAX);
 		if (resolved_len >= PATH_MAX) {
-			if (m)
-				free(resolved);
 			errno = ENAMETOOLONG;
 			return (NULL);
 		}
-		if (lstat(resolved, &sb) != 0) {
-			if (m)
-				free(resolved);
+		if (lstat(resolved, &sb) != 0)
 			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));
 			if (slen <= 0 || slen >= sizeof(symlink)) {
-				if (m)
-					free(resolved);
 				if (slen < 0) {
 					/* keep errno from readlink(2) call */
 				} else if (slen == 0) {
@@ -207,8 +174,6 @@ realpath(const char * __restrict path, c
 			if (p != NULL) {
 				if (symlink[slen - 1] != '/') {
 					if (slen + 1 >= sizeof(symlink)) {
-						if (m)
-							free(resolved);
 						errno = ENAMETOOLONG;
 						return (NULL);
 					}
@@ -218,16 +183,12 @@ realpath(const char * __restrict path, c
 				left_len = strlcat(symlink, left,
 				    sizeof(symlink));
 				if (left_len >= sizeof(symlink)) {
-					if (m)
-						free(resolved);
 					errno = ENAMETOOLONG;
 					return (NULL);
 				}
 			}
 			left_len = strlcpy(left, symlink, sizeof(left));
 		} else if (!S_ISDIR(sb.st_mode) && p != NULL) {
-			if (m)
-				free(resolved);
 			errno = ENOTDIR;
 			return (NULL);
 		}
@@ -241,3 +202,29 @@ realpath(const char * __restrict path, c
 		resolved[resolved_len - 1] = '\0';
 	return (resolved);
 }
+
+char *
+realpath(const char * __restrict path, char * __restrict resolved)
+{
+	char *m, *res;
+
+	if (path == NULL) {
+		errno = EINVAL;
+		return (NULL);
+	}
+	if (path[0] == '\0') {
+		errno = ENOENT;
+		return (NULL);
+	}
+	if (resolved != NULL) {
+		m = NULL;
+	} else {
+		m = resolved = malloc(PATH_MAX);
+		if (resolved == NULL)
+			return (NULL);
+	}
+	res = realpath1(path, resolved);
+	if (res == NULL)
+		free(m);
+	return (res);
+}

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