mod_mimeparse: Don't close file descriptor already closed by GMime.

New warnings about closing file descriptors that were already closed
alerted to a file descriptor we were trying to close after the library
had already closed it for us. Since that isn't captured in the array
in fd.c, add an API to indicate a file descriptor has already been
closed outside of the BBS (e.g. in a library), so we can keep our state
up to date while avoiding double closes.

Author: InterLinked1

bbs/fd.c

@@ -398,16 +398,17 @@ int __bbs_close(int fd, const char *file, int line, const char *func)
 
 	/* Detect attempts to close file descriptors we shouldn't be closing
 	 * (e.g. can happen if a file descriptor variable is initialized to 0 instead of -1) */
-	if (fd <= 2 && (fd < 0 || strcmp(file, "system.c"))) { /* It's legitimate to close file descriptors 0, 1, and 2 when calling exec */
+	if (unlikely(fd <= 2) && (fd < 0 || strcmp(file, "system.c"))) { /* It's legitimate to close file descriptors 0, 1, and 2 when calling exec */
 		bbs_warning("Attempting to close file descriptor %d at %s:%d (%s)\n", fd, file, line, func);
 		bbs_log_backtrace(); /* Get a backtrace to see what made the invalid close, in case immediate caller isn't enough detail. */
 	}
 	res = close(fd);
 	if (res) {
 		if (errno == EBADF && ARRAY_IN_BOUNDS(fd, fdleaks)) {
-			__bbs_log(LOG_WARNING, 0, file, line, func, "Failed to close file descriptor %d: %s (previously closed at %s:%d)\n", fd, strerror(errno), fdleaks[fd].file, fdleaks[fd].line);
+			__bbs_log(LOG_WARNING, 0, file, line, func, "Failed to close fd %d: %s (previously %s at %s:%d)\n",
+				fd, strerror(errno), fdleaks[fd].isopen ? "opened" : "closed", fdleaks[fd].file, fdleaks[fd].line);
 		} else {
-			__bbs_log(LOG_WARNING, 0, file, line, func, "Failed to close file descriptor %d: %s\n", fd, strerror(errno));
+			__bbs_log(LOG_WARNING, 0, file, line, func, "Failed to close fd %d: %s\n", fd, strerror(errno));
 		}
 	} else if (ARRAY_IN_BOUNDS(fd, fdleaks)) { /* && !res (implicit) */
 		fdleaks[fd].isopen = 0;
@@ -417,7 +418,27 @@ int __bbs_close(int fd, const char *file, int line, const char *func)
 	}
 	FD_LOGF("%lu: %s:%d (%s) close(%d)\n", time(NULL), file, line, func, fd);
 	return res;
-}	
+}
+
+/* gcc thinks func is unused in this function? */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+int __bbs_mark_closed(int fd, const char *file, int line, const char *func)
+{
+	/* Don't attempt to close the file descriptor, if it's already closed.
+	 * Something else may reuse it in the meantime and we could close something else.
+	 * Of course, if that's the case, we'll mess up our state array below,
+	 * but that's lower stakes than actually messing up program behavior. */
+	if (ARRAY_IN_BOUNDS(fd, fdleaks)) {
+		fdleaks[fd].isopen = 0;
+		/* Update to where it was closed so we can debug attempts to close previously closed fds */
+		COPY(fdleaks[fd].file, file);
+		fdleaks[fd].line = line;
+	}
+	FD_LOGF("%lu: %s:%d (%s) mark_closed(%d)\n", time(NULL), file, line, func, fd);
+	return 0;
+}
+#pragma GCC diagnostic pop
 
 FILE *__bbs_fopen(const char *path, const char *mode, const char *file, int line, const char *func)
 {

include/bbs.h

@@ -132,13 +132,20 @@
 #define dup(a)		__bbs_dup(a, __FILE__,__LINE__,__func__)
 #define eventfd(a,b)	__bbs_eventfd(a, b, __FILE__,__LINE__,__func__)
 
+/*! \brief Mark a file descriptor as closed. This is useful if
+ * a file descriptor was opened by the BBS and closed by another library,
+ * so we can keep the internal state table of file descriptors synchronized.
+ * This function takes you at your word, so be sure it really is closed! */
+#define bbs_mark_closed(f) __bbs_mark_closed(f, __FILE__,__LINE__,__func__)
+
 int __bbs_open(const char *file, int line, const char *func, const char *path, int flags, ...);
 int __bbs_pipe(int *fds, const char *file, int line, const char *func);
 int __bbs_socketpair(int domain, int type, int protocol, int sv[2], const char *file, int line, const char *func);
 int __bbs_socket(int domain, int type, int protocol, const char *file, int line, const char *func);
 int __bbs_accept(int socket, struct sockaddr *address, socklen_t *address_len, const char *file, int line, const char *func);
 int __bbs_eventfd(unsigned int initval, int flags, const char *file, int line, const char *func);
 int __bbs_close(int fd, const char *file, int line, const char *func);
+int __bbs_mark_closed(int fd, const char *file, int line, const char *func);
 FILE *__bbs_fopen(const char *path, const char *mode, const char *file, int line, const char *func);
 int __bbs_fclose(FILE *ptr);
 int __bbs_dup2(int oldfd, int newfd, const char *file, int line, const char *func);

modules/mod_mimeparse.c

@@ -366,7 +366,7 @@ static GMimeMessage *mk_mime(const char *file)
 	message = g_mime_parser_construct_message(parser, NULL);
 
 	g_object_unref(parser);
-	close(fd);
+	bbs_mark_closed(fd); /* g_object_unref closed our file descriptor for us */
 
 	if (!message) {
 		bbs_error("Failed to parse message %s as MIME\n", file);