[configfile] fix reading uninitialized variable (found by Willian B.)

- stream_open()-ing an empty file shouldn't return an error (and didn't on my
  system)
- don't try to handle empty file as non-error in config_parse_file;
  this fixes the read of an potentially unitialized variable
- stream_open()-ing an empty file doesn't try to map the file anymore
  and should not result in any errors; return an empty stream instead.
- stream_open(): make sure the returned stream is always initialized
  correctly, and can always be used with stream_close(), whether opening
  was successful or not
- stream_close(): also reset the size member

From: Stefan Bühler <stbuehler@web.de>

git-svn-id: svn://svn.lighttpd.net/lighttpd/branches/lighttpd-1.4.x@3003 152afb58-edef-0310-8abb-c4023f1b3aa9

NEWS

@@ -28,6 +28,7 @@ NEWS
   * fix segfault when temp file for upload couldn't be created (found by coverity)
   * mime.conf: add some new mime types, remove .dat, .sha1, .md5, update .vcf
   * [mod_proxy] add unix domain socket support (fixes #2653)
+  * [configfile] fix reading uninitialized variable (found by Willian B.)
 
 - 1.4.35 - 2014-03-12
   * [network/ssl] fix build error if TLSEXT is disabled

src/configfile.c

@@ -996,14 +996,9 @@ int config_parse_file(server *srv, config_t *context, const char *fn) {
 	}
 
 	if (0 != stream_open(&s, filename)) {
-		if (s.size == 0) {
-			/* the file was empty, nothing to parse */
-			ret = 0;
-		} else {
-			log_error_write(srv, __FILE__, __LINE__, "sbss",
-					"opening configfile ", filename, "failed:", strerror(errno));
-			ret = -1;
-		} 
+		log_error_write(srv, __FILE__, __LINE__, "sbss",
+				"opening configfile ", filename, "failed:", strerror(errno));
+		ret = -1;
 	} else {
 		tokenizer_init(&t, filename, s.start, s.size);
 		ret = config_parse(srv, context, &t);

src/stream.c

@@ -22,23 +22,28 @@ int stream_open(stream *f, buffer *fn) {
 #endif
 
 	f->start = NULL;
+	f->size = 0;
 
 	if (-1 == stat(fn->ptr, &st)) {
 		return -1;
 	}
 
-	f->size = st.st_size;
+	if (0 == st.st_size) {
+		/* empty file doesn't need a mapping */
+		return 0;
+	}
 
 #ifdef HAVE_MMAP
 	if (-1 == (fd = open(fn->ptr, O_RDONLY | O_BINARY))) {
 		return -1;
 	}
 
-	f->start = mmap(NULL, f->size, PROT_READ, MAP_SHARED, fd, 0);
+	f->start = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, fd, 0);
 
 	close(fd);
 
 	if (MAP_FAILED == f->start) {
+		f->start = NULL;
 		return -1;
 	}
 
@@ -56,8 +61,8 @@ int stream_open(stream *f, buffer *fn) {
 	mh = CreateFileMapping( fh,
 			NULL,
 			PAGE_READONLY,
-			(sizeof(off_t) > 4) ? f->size >> 32 : 0,
-			f->size & 0xffffffff,
+			(sizeof(off_t) > 4) ? st.st_size >> 32 : 0,
+			st.st_size & 0xffffffff,
 			NULL);
 
 	if (!mh) {
@@ -88,6 +93,8 @@ int stream_open(stream *f, buffer *fn) {
 # error no mmap found
 #endif
 
+	f->size = st.st_size;
+
 	return 0;
 }
 
@@ -99,6 +106,7 @@ int stream_close(stream *f) {
 #endif
 
 	f->start = NULL;
+	f->size = 0;
 
 	return 0;
 }