From bc6b256c343893b7b579baddeee140f22777537c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20B=C3=BChler?= <stbuehler@lighttpd.net>
Date: Sat, 29 Jul 2017 15:21:08 +0200
Subject: [PATCH] [core] use readdir instead of readdir_r

readdir_r is deprecated in glibc due to serious memory handling issues
in the API: one cannot pass the size of the allocated dirent.

glibc authors claims readdir is thread-safe in modern implementations,
and expect POSIX to require it in a future version.

No way to check whether readdir is thread-safe though :(

("thread-safe" in this context means different directory streams, which
is good enough.)

Also remove li_dirent_buf_size.

Change-Id: Ia5eae3327e97dc4b0751fb2604ea21c0ce09a5f9
---
 include/lighttpd/utils.h |  2 --
 src/common/utils.c       | 30 ------------------------------
 src/main/stat_cache.c    | 21 ++++++++++-----------
 3 files changed, 10 insertions(+), 43 deletions(-)

diff --git a/include/lighttpd/utils.h b/include/lighttpd/utils.h
index 00df9c4..39f4a91 100644
--- a/include/lighttpd/utils.h
+++ b/include/lighttpd/utils.h
@@ -81,8 +81,6 @@ LI_API gboolean li_string_suffix(const GString *str, const gchar *s, gsize len);
 
 LI_API void li_string_append_int(GString *dest, gint64 val);
 
-LI_API gsize li_dirent_buf_size(DIR * dirp);
-
 LI_API void li_apr_sha1_base64(GString *dest, const GString *passwd);
 LI_API void li_apr_md5_crypt(GString *dest, const GString *password, const GString *salt);
 
diff --git a/src/common/utils.c b/src/common/utils.c
index 06f57d4..70c7904 100644
--- a/src/common/utils.c
+++ b/src/common/utils.c
@@ -851,36 +851,6 @@ void li_string_append_int(GString *dest, gint64 v) {
 	dest->len = len;
 }
 
-/* http://womble.decadentplace.org.uk/readdir_r-advisory.html */
-gsize li_dirent_buf_size(DIR * dirp) {
-	glong name_max;
- 	gsize name_end;
-
-#	if !defined(HAVE_DIRFD)
-		UNUSED(dirp);
-#	endif
-
-#	if defined(HAVE_FPATHCONF) && defined(HAVE_DIRFD) && defined(_PC_NAME_MAX)
-		name_max = fpathconf(dirfd(dirp), _PC_NAME_MAX);
-		if (name_max == -1)
-#			if defined(NAME_MAX)
-				name_max = (NAME_MAX > 255) ? NAME_MAX : 255;
-#			else
-				return (gsize)(-1);
-#			endif
-#	else
-#		if defined(NAME_MAX)
-			name_max = (NAME_MAX > 255) ? NAME_MAX : 255;
-#		else
-#			error "buffer size for readdir_r cannot be determined"
-#		endif
-#	endif
-
-    name_end = (gsize)offsetof(struct dirent, d_name) + name_max + 1;
-
-    return (name_end > sizeof(struct dirent) ? name_end : sizeof(struct dirent));
-}
-
 const char *li_remove_path(const char *path) {
 	char *p = strrchr(path, G_DIR_SEPARATOR);
 	if (NULL != p && *(p) != '\0') {
diff --git a/src/main/stat_cache.c b/src/main/stat_cache.c
index 8d5998c..506e712 100644
--- a/src/main/stat_cache.c
+++ b/src/main/stat_cache.c
@@ -108,10 +108,7 @@ static void stat_cache_run(gpointer data) {
 	if (!sce->data.failed && sce->type == STAT_CACHE_ENTRY_DIR) {
 		/* dirlisting */
 		DIR *dirp;
-		gsize size;
-		struct dirent *entry;
 		struct dirent *result;
-		gint error;
 		liStatCacheEntryData sced;
 		GString *str;
 
@@ -120,16 +117,19 @@ static void stat_cache_run(gpointer data) {
 			sce->data.failed = TRUE;
 			sce->data.err = errno;
 		} else {
-			size = li_dirent_buf_size(dirp);
-			LI_FORCE_ASSERT(size != (gsize)-1);
-			entry = g_slice_alloc(size);
-
 			sce->dirlist = g_array_sized_new(FALSE, FALSE, sizeof(liStatCacheEntryData), 32);
 
 			str = g_string_sized_new(sce->data.path->len + 64);
 			g_string_append_len(str, GSTR_LEN(sce->data.path));
 
-			while ((error = readdir_r(dirp, entry, &result)) == 0 && result != NULL) {
+			/* glibc claims modern readdir are thread-safe, and
+			 * readdir_r has issues. no way to check readdir is actually
+			 * safe, hope for the best.
+			 */
+			for (;;) {
+				errno = 0; /* readdir may not reset errno */
+				if (NULL == (result = readdir(dirp))) break;
+
 				/* hide "." and ".." */
 				if (result->d_name[0] == '.' && (result->d_name[1] == '\0' ||
 					(result->d_name[1] == '.' && result->d_name[2] == '\0'))) {
@@ -155,13 +155,12 @@ static void stat_cache_run(gpointer data) {
 				g_array_append_val(sce->dirlist, sced);
 			}
 
-			if (error) {
+			if (errno) {
 				sce->data.failed = TRUE;
-				sce->data.err = error;
+				sce->data.err = errno;
 			}
 
 			g_string_free(str, TRUE);
-			g_slice_free1(size, entry);
 			closedir(dirp);
 		}
 	}