flist/xattrs/generator/uidlist/clientserver: plug audit-reported leaks

Five error-path/cleanup memory leaks found by an external audit:

- flist.c send_file_name: free the ACL loaded by get_acl() when a later
  get_xattr() fails (and on the get_acl error path).
- xattrs.c copy_xattrs: free the xattr datum buffer when the setxattr fails.
- generator.c recv_generator: free real_sx at the cleanup label (the
  directory branch loaded its ACL via set_file_attrs but only the
  regular-file path freed it); zero-init real_sx so the early gotos are safe.
- uidlist.c send_one_list: free the strdup'd id-0 name after send_one_name.
- clientserver.c start_inband_exchange: free modname on the early error
  returns (it was freed only on the success path).

ASan/LSan regression tests cover the generator, uidlist and clientserver
leaks; the flist and xattrs leaks need a forced syscall failure and are
covered by the audit's standalone harnesses.

Reported-by: Leonid Bugaev <leonsbox@gmail.com>
(cherry picked from commit 078f3b99f4004510d418ee9d97d9b775dc8587bc)

clientserver.c

@@ -273,8 +273,10 @@ int start_inband_exchange(int f_in, int f_out, const char *user, int argc, char
 	if (!user)
 		user = getenv("LOGNAME");
 
-	if (exchange_protocols(f_in, f_out, line, sizeof line, 1) < 0)
+	if (exchange_protocols(f_in, f_out, line, sizeof line, 1) < 0) {
+		free(modname);
 		return -1;
+	}
 
 	if (early_input_file) {
 		STRUCT_STAT st;
@@ -285,11 +287,16 @@ int start_inband_exchange(int f_in, int f_out, const char *user, int argc, char
 		if (!f && ei_fd >= 0) close(ei_fd);
 		if (!f || do_fstat(fileno(f), &st) < 0) {
 			rsyserr(FERROR, errno, "failed to open %s", early_input_file);
+			if (f)
+				fclose(f);
+			free(modname);
 			return -1;
 		}
 		early_input_len = st.st_size;
 		if (early_input_len > (int)sizeof line) {
 			rprintf(FERROR, "%s is > %d bytes.\n", early_input_file, (int)sizeof line);
+			fclose(f);
+			free(modname);
 			return -1;
 		}
 		if (early_input_len > 0) {
@@ -298,6 +305,8 @@ int start_inband_exchange(int f_in, int f_out, const char *user, int argc, char
 				int len;
 				if (feof(f)) {
 					rprintf(FERROR, "Early EOF in %s\n", early_input_file);
+					fclose(f);
+					free(modname);
 					return -1;
 				}
 				len = fread(line, 1, early_input_len, f);
@@ -374,6 +383,7 @@ int start_inband_exchange(int f_in, int f_out, const char *user, int argc, char
 	while (1) {
 		if (!read_line_old(f_in, line, sizeof line, 0)) {
 			rprintf(FERROR, "rsync: didn't get server startup line\n");
+			free(modname);
 			return -1;
 		}
 
@@ -397,6 +407,7 @@ int start_inband_exchange(int f_in, int f_out, const char *user, int argc, char
 			rprintf(FERROR, "%s\n", line);
 			/* This is always fatal; the server will now
 			 * close the socket. */
+			free(modname);
 			return -1;
 		}
 

flist.c

@@ -1794,6 +1794,7 @@ static struct file_struct *send_file_name(int f, struct file_list *flist,
 			sx.st.st_mode = file->mode;
 			if (get_acl(fname, &sx) < 0) {
 				io_error |= IOERR_GENERAL;
+				free_acl(&sx);
 				return NULL;
 			}
 		}
@@ -1803,6 +1804,9 @@ static struct file_struct *send_file_name(int f, struct file_list *flist,
 			sx.st.st_mode = file->mode;
 			if (get_xattr(fname, &sx) < 0) {
 				io_error |= IOERR_GENERAL;
+#ifdef SUPPORT_ACLS
+				free_acl(&sx); /* get_acl() above may have loaded one */
+#endif
 				return NULL;
 			}
 		}

generator.c

@@ -1385,7 +1385,7 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 	static int need_fuzzy_dirlist = 0;
 	struct file_struct *fuzzy_file = NULL;
 	int fd = -1, f_copy = -1;
-	stat_x sx = {0}, real_sx;
+	stat_x sx = {0}, real_sx = {0};
 	STRUCT_STAT partial_st;
 	struct file_struct *back_file = NULL;
 	int statret, real_ret, stat_errno;
@@ -2186,6 +2186,7 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
 	}
 
 	free_stat_x(&sx);
+	free_stat_x(&real_sx);
 }
 
 /* If we are replacing an existing hard link, symlink, device, or special file,

uidlist.c

@@ -397,9 +397,11 @@ static void send_one_list(int f, struct idlist *idlist, int usernames)
 
 	/* Terminate the uid list with 0 (which was excluded above).
 	 * A modern rsync also sends the name of id 0. */
-	if (xmit_id0_names)
-		send_one_name(f, 0, usernames ? uid_to_user(0) : gid_to_group(0));
-	else
+	if (xmit_id0_names) {
+		const char *name = usernames ? uid_to_user(0) : gid_to_group(0);
+		send_one_name(f, 0, name);
+		free((char *)name);
+	} else
 		write_varint30(f, 0);
 }
 

xattrs.c

@@ -381,6 +381,7 @@ int copy_xattrs(const char *source, const char *dest, int dest_fd)
 				"copy_xattrs: %ssetxattr(%s,\"%s\") failed",
 				dest_fd >= 0 ? "f" : "l", full_fname(dest), name);
 			errno = save_errno;
+			free(ptr);
 			return -1;
 		}
 		free(ptr);