conf: don't setup shared mountpoint for shmounts

Leave it up to the caller for now until we have a clear way to do
this without causing double mounts etc.

Needed-by: https://github.com/lxc/lxd/issues/5227

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/confile.c

@@ -1788,24 +1788,31 @@ static int set_config_mount_auto(const char *key, const char *value,
 		lxc_conf->auto_mounts |= allowed_auto_mounts[i].flag;
 
 		if (is_shmounts) {
-			char *slide = token + STRLITERALLEN("shmounts:");
+			char *container_path;
+			char *host_path;
 
-			if (*slide == '\0') {
+			host_path = token + STRLITERALLEN("shmounts:");
+			if (*host_path == '\0') {
 				SYSERROR("Failed to copy shmounts host path");
 				goto on_error;
 			}
 
-			lxc_conf->shmount.path_host = strdup(slide);
+			container_path = strchr(host_path, ':');
+			if (!container_path || *(container_path + 1) == '\0')
+				container_path = "/dev/.lxc-mounts";
+			else
+				*container_path++ = '\0';
+
+			ERROR("AAAA: %s", host_path);
+			ERROR("BBBB: %s", container_path);
+
+			lxc_conf->shmount.path_host = strdup(host_path);
 			if (!lxc_conf->shmount.path_host) {
 				SYSERROR("Failed to copy shmounts host path");
 				goto on_error;
 			}
 
-			slide = strchr(slide, ':');
-			if (!slide || *(++slide) == '\0')
-				slide = "/dev/.lxc-mounts";
-
-			lxc_conf->shmount.path_cont = strdup(slide);
+			lxc_conf->shmount.path_cont = strdup(container_path);
 			if(!lxc_conf->shmount.path_cont) {
 				SYSERROR("Failed to copy shmounts container path");
 				goto on_error;

src/lxc/start.c

@@ -1578,75 +1578,6 @@ static inline int do_share_ns(void *arg)
 	return 0;
 }
 
-static int lxc_setup_shmount(struct lxc_conf *conf)
-{
-	size_t len_cont;
-	char *full_cont_path;
-	int ret = -1;
-
-	/* Construct the shmount path under the container root. */
-	len_cont = strlen(conf->rootfs.mount) + 1 + strlen(conf->shmount.path_cont);
-	/* +1 for the terminating '\0' */
-	full_cont_path = malloc(len_cont + 1);
-	if (!full_cont_path) {
-		SYSERROR("Not enough memory");
-		return -ENOMEM;
-	}
-
-	ret = snprintf(full_cont_path, len_cont + 1, "%s/%s",
-		       conf->rootfs.mount, conf->shmount.path_cont);
-	if (ret < 0 || ret >= len_cont + 1) {
-		SYSERROR("Failed to create filename");
-		free(full_cont_path);
-		return -1;
-	}
-
-	/* Check if shmount point is already set up. */
-	if (is_shared_mountpoint(conf->shmount.path_host)) {
-		INFO("Path \"%s\" is already MS_SHARED. Reusing",
-		     conf->shmount.path_host);
-		free(full_cont_path);
-		return 0;
-	}
-
-	/* Create host and cont mount paths */
-	ret = mkdir_p(conf->shmount.path_host, 0711);
-	if (ret < 0 && errno != EEXIST) {
-		SYSERROR("Failed to create directory \"%s\"",
-			 conf->shmount.path_host);
-		free(full_cont_path);
-		return ret;
-	}
-
-	ret = mkdir_p(full_cont_path, 0711);
-	if (ret < 0 && errno != EEXIST) {
-		SYSERROR("Failed to create directory \"%s\"", full_cont_path);
-		free(full_cont_path);
-		return ret;
-	}
-
-	/* Prepare host mountpoint */
-	ret = mount("tmpfs", conf->shmount.path_host, "tmpfs", 0,
-		    "size=100k,mode=0711");
-	if (ret < 0) {
-		SYSERROR("Failed to mount \"%s\"", conf->shmount.path_host);
-		free(full_cont_path);
-		return ret;
-	}
-
-	ret = mount(conf->shmount.path_host, conf->shmount.path_host, "none",
-		    MS_REC | MS_SHARED, "");
-	if (ret < 0) {
-		SYSERROR("Failed to make shared \"%s\"", conf->shmount.path_host);
-		free(full_cont_path);
-		return ret;
-	}
-
-	INFO("Setup shared mount point \"%s\"", conf->shmount.path_host);
-	free(full_cont_path);
-	return 0;
-}
-
 /* lxc_spawn() performs crucial setup tasks and clone()s the new process which
  * exec()s the requested container binary.
  * Note that lxc_spawn() runs in the parent namespaces. Any operations performed
@@ -1693,17 +1624,6 @@ static int lxc_spawn(struct lxc_handler *handler)
 	if (ret < 0)
 		goto out_sync_fini;
 
-	if (conf->shmount.path_host) {
-		if (!conf->shmount.path_cont)
-			goto out_sync_fini;
-
-		ret = lxc_setup_shmount(conf);
-		if (ret < 0) {
-			ERROR("Failed to setup shared mount point");
-			goto out_sync_fini;
-		}
-	}
-
 	if (handler->ns_clone_flags & CLONE_NEWNET) {
 		if (!lxc_list_empty(&conf->network)) {
 

src/tests/mount_injection.c

@@ -386,16 +386,54 @@ static int do_unpriv_container_test()
 	return perform_container_test(NAME"unprivileged", config_items);
 }
 
+static bool lxc_setup_shmount(const char *shmount_path)
+{
+	int ret;
+
+	ret = mkdir_p(shmount_path, 0711);
+	if (ret < 0 && errno != EEXIST) {
+		fprintf(stderr, "Failed to create directory \"%s\"\n", shmount_path);
+		return false;
+	}
+
+	/* Prepare host mountpoint */
+	ret = mount("tmpfs", shmount_path, "tmpfs", 0, "size=100k,mode=0711");
+	if (ret < 0) {
+		fprintf(stderr, "Failed to mount \"%s\"\n", shmount_path);
+		return false;
+	}
+
+	ret = mount(shmount_path, shmount_path, "none", MS_REC | MS_SHARED, "");
+	if (ret < 0) {
+		fprintf(stderr, "Failed to make shared \"%s\"\n", shmount_path);
+		return false;
+	}
+
+	return true;
+}
+
+static void lxc_teardown_shmount(char *shmount_path)
+{
+	(void)umount2(shmount_path, MNT_DETACH);
+	(void)recursive_destroy(shmount_path);
+}
+
 int main(int argc, char *argv[])
 {
+	if (!lxc_setup_shmount("/tmp/mount_injection_test"))
+		exit(EXIT_FAILURE);
+
 	if (do_priv_container_test()) {
 		fprintf(stderr, "Privileged mount injection test failed\n");
-		return -1;
+		exit(EXIT_FAILURE);
 	}
 
-	if(do_unpriv_container_test()) {
+	if (do_unpriv_container_test()) {
 		fprintf(stderr, "Unprivileged mount injection test failed\n");
-		return -1;
+		exit(EXIT_FAILURE);
 	}
-	return 0;
+
+	lxc_teardown_shmount("/tmp/mount_injection_test");
+
+	exit(EXIT_SUCCESS);
 }