librc: clear dirfds when creating new svcdir

if for whatever reason, /run/openrc exists in the rootfs before first
boot, we'd still end up with an invalid fd. while users are not really
supposed to have anything in /run (under the tmpfs mount), should they
do, it's better to not fail

clearing the dirfds as we create svcdir also means we don't need a new
librc api function to clear it, for now at least.

Author: navi-desu

src/librc/librc-depend.c

@@ -693,7 +693,9 @@ rc_deptree_update_needed(time_t *newest, char *file)
 
 	/* Quick test to see if anything we use has changed and we have
 	 * data in our deptree. */
-	if (mkdir(rc_svcdir(), 0755) != 0 && errno != EEXIST)
+	if (mkdir(rc_svcdir(), 0755) == 0)
+		clear_dirfds(); /* clear our cached dirfds if we created a new svcdir, as a sanity check */
+	else if (errno != EEXIST)
 		fprintf(stderr, "mkdir '%s': %s\n", rc_svcdir(), strerror(errno));
 
 	if (fstatat(rc_dirfd(RC_DIR_SVCDIR), "deptree", &buf, 0) == 0) {

src/librc/librc.c

@@ -80,6 +80,18 @@ int rc_dirfd(enum rc_dir dir) {
 	return dirfds[dir];
 }
 
+void clear_dirfds(void) {
+	for (size_t i = 0; i < RC_DIR_MAX; i++) {
+		/* dirfd is zero-initialized, though zero is a valid
+		 * FD, dirfd should never contain FDs which are <= 2. */
+		if (dirfds[i] <= 0)
+			continue;
+
+		close(dirfds[i]);
+		dirfds[i] = -1;
+	}
+}
+
 #define LS_INITD	0x01
 #define LS_DIR		0x02
 static RC_STRINGLIST *
@@ -633,15 +645,7 @@ rc_set_user(void)
 	rc_dirs.scriptdirs[SCRIPTDIR_USR] = rc_dirs.usrconfdir;
 	rc_dirs.scriptdirs[SCRIPTDIR_SVC] = rc_dirs.svcdir;
 
-	for (size_t i = 0; i < RC_DIR_MAX; i++) {
-		/* dirfd is zero-initialized, though zero is a valid
-		 * FD, dirfd should never contain FDs which are <= 2. */
-		if (dirfds[i] <= 0)
-			continue;
-
-		close(dirfds[i]);
-		dirfds[i] = -1;
-	}
+	clear_dirfds();
 }
 
 const char * const *

src/librc/librc.h

@@ -73,5 +73,6 @@ static const char *const dirnames[RC_DIR_SYS_MAX] =
 };
 
 RC_STRINGLIST *config_list(int dirfd, const char *pathname);
+void clear_dirfds(void);
 
 #endif