From cd1ef5d3a621d773f553a0acb131abec8a3b18a1 Mon Sep 17 00:00:00 2001
From: guenther <guenther@openbsd.org>
Date: Sun, 28 Aug 2016 04:08:59 +0000
Subject: [PATCH] Don't call lstat() before readlink() just to see if it's a
 symlink, as readlink() will tell you that more cheaply.

ok millert@
---
 lib/libc/stdlib/realpath.c  | 31 ++++++++++++++++--------------
 libexec/ld.so/dl_realpath.c | 38 ++++++++++++++++++++-----------------
 2 files changed, 38 insertions(+), 31 deletions(-)

diff --git a/lib/libc/stdlib/realpath.c b/lib/libc/stdlib/realpath.c
index 27f1a29061d..c691252ccf5 100644
--- a/lib/libc/stdlib/realpath.c
+++ b/lib/libc/stdlib/realpath.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: realpath.c,v 1.20 2015/10/13 20:55:37 millert Exp $ */
+/*	$OpenBSD: realpath.c,v 1.21 2016/08/28 04:08:59 guenther Exp $ */
 /*
  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
  *
@@ -27,8 +27,6 @@
  * SUCH DAMAGE.
  */
 
-#include <sys/stat.h>
-
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -47,7 +45,6 @@
 char *
 realpath(const char *path, char *resolved)
 {
-	struct stat sb;
 	char *p, *q, *s;
 	size_t left_len, resolved_len;
 	unsigned symlinks;
@@ -148,21 +145,27 @@ realpath(const char *path, char *resolved)
 			errno = ENAMETOOLONG;
 			goto err;
 		}
-		if (lstat(resolved, &sb) != 0) {
-			if (errno == ENOENT && p == NULL) {
-				errno = serrno;
-				return (resolved);
+		slen = readlink(resolved, symlink, sizeof(symlink) - 1);
+		if (slen < 0) {
+			switch (errno) {
+			case EINVAL:
+				/* not a symlink, continue to next component */
+				continue;
+			case ENOENT:
+				if (p == NULL) {
+					errno = serrno;
+					return (resolved);
+				}
+				/* FALLTHROUGH */
+			default:
+				goto err;
 			}
-			goto err;
-		}
-		if (S_ISLNK(sb.st_mode)) {
+		} else {
 			if (symlinks++ > SYMLOOP_MAX) {
 				errno = ELOOP;
 				goto err;
 			}
-			slen = readlink(resolved, symlink, sizeof(symlink) - 1);
-			if (slen < 0)
-				goto err;
+
 			symlink[slen] = '\0';
 			if (symlink[0] == '/') {
 				resolved[1] = 0;
diff --git a/libexec/ld.so/dl_realpath.c b/libexec/ld.so/dl_realpath.c
index 498ee3ca054..91a86686b87 100644
--- a/libexec/ld.so/dl_realpath.c
+++ b/libexec/ld.so/dl_realpath.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dl_realpath.c,v 1.3 2014/10/19 03:56:28 doug Exp $ */
+/*	$OpenBSD: dl_realpath.c,v 1.4 2016/08/28 04:08:59 guenther Exp $ */
 /*
  * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
  *
@@ -28,11 +28,10 @@
  */
 
 #include <sys/types.h>
+#include <sys/errno.h>
 #include <limits.h>
 #include "archdep.h"
 
-#define ENOENT -2
-
 /*
  * This file was copied from libc/stdlib/realpath.c and modified for ld.so's
  * syscall method which returns -errno.
@@ -48,12 +47,11 @@
 char *
 _dl_realpath(const char *path, char *resolved)
 {
-	struct stat sb;
 	const char *p, *s;
 	char *q;
 	size_t left_len, resolved_len;
 	unsigned symlinks;
-	int slen, mem_allocated, ret;
+	int slen, mem_allocated;
 	char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX];
 
 	if (path[0] == '\0') {
@@ -135,27 +133,33 @@ _dl_realpath(const char *path, char *resolved)
 		}
 
 		/*
-		 * Append the next path component and lstat() it. If
-		 * lstat() fails we still can return successfully if
-		 * there are no more path components left.
+		 * Append the next path component and readlink() it. If
+		 * readlink() fails we still can return successfully if
+		 * it wasn't a exists but isn't a symlink, or if there
+		 * are no more path components left.
 		 */
 		resolved_len = _dl_strlcat(resolved, next_token, PATH_MAX);
 		if (resolved_len >= PATH_MAX) {
 			goto err;
 		}
-		if ((ret = _dl_lstat(resolved, &sb)) != 0) {
-			if (ret == ENOENT && p == NULL) {
-				return (resolved);
+		slen = _dl_readlink(resolved, symlink, sizeof(symlink) - 1);
+		if (slen < 0) {
+			switch (slen) {
+			case -EINVAL:
+				/* not a symlink, continue to next component */
+				continue;
+			case -ENOENT:
+				if (p == NULL)
+					return (resolved);
+				/* FALLTHROUGH */
+			default:
+				goto err;
 			}
-			goto err;
-		}
-		if (S_ISLNK(sb.st_mode)) {
+		} else {
 			if (symlinks++ > SYMLOOP_MAX) {
 				goto err;
 			}
-			slen = _dl_readlink(resolved, symlink, sizeof(symlink) - 1);
-			if (slen < 0)
-				goto err;
+
 			symlink[slen] = '\0';
 			if (symlink[0] == '/') {
 				resolved[1] = 0;
-- 
2.20.1