From: Tom Hromatka <tom.hromatka@oracle.com>
Date: Thu, 11 May 2023 19:53:18 +0000 (-0600)
Subject: api: Delete the cgroup if cgroup_create_cgroup() fails
X-Git-Tag: v3.1.0~70
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6d44f253d9e55e6b2095ae50d216137e9a2e481a;p=thirdparty%2Flibcgroup.git

api: Delete the cgroup if cgroup_create_cgroup() fails

cgroup_create_cgroup() loops through the controllers in struct cgroup
and creates the requested cgroups.  Some controllers could succeed
before a controller fails.  This results in a case where the cgroup
directory has been created and remains in /sys/fs/cgroup even after a
failure.

Invoke cgroup_delete_cgroup() after we fail to create a cgroup under a
controller.  This will delete the cgroup directory if it had been
created and put the system (nearly) back to its original state.  (It's
possible that the parent cgroup's subtree_control file was modified and
not restored, but that's best fixed in another patch.)

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
---

diff --git a/src/api.c b/src/api.c
index 9b830720..c30ac98b 100644
--- a/src/api.c
+++ b/src/api.c
@@ -2909,6 +2909,11 @@ int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
 		/* Create an empty cgroup v2 cgroup */
 		error = _cgroup_create_cgroup(cgroup, NULL, ignore_ownership);
 		if (error)
+			/*
+			 * Since we only attempted to create a single cgroup,
+			 * _cgroup_create_cgroup() can capably undo the failure and no
+			 * interventions are required here.
+			 */
 			return error;
 	}
 
@@ -2919,8 +2924,21 @@ int cgroup_create_cgroup(struct cgroup *cgroup, int ignore_ownership)
 	 */
 	for (i = 0; i < cgroup->index; i++) {
 		error = _cgroup_create_cgroup(cgroup, cgroup->controller[i], ignore_ownership);
-		if (error)
+		if (error) {
+			int del_error;
+
+			/*
+			 * This will remove any cgroup directories that were made, but it won't
+			 * undo changes that have been written to the parent cgroup's
+			 * subtree_control file.  To safely undo changes there, we would need to
+			 * save the subtree_control file's previous value and restore it.
+			 */
+			del_error = cgroup_delete_cgroup(cgroup, 1);
+			if (del_error)
+				cgroup_err("Failed to delete %s: %s\n", cgroup->name,
+					   cgroup_strerror(del_error));
 			return error;
+		}
 	}
 
 	return 0;
diff --git a/src/config.c b/src/config.c
index 9fcfc032..80c09ece 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1221,6 +1221,7 @@ int cgroup_config_load_config(const char *pathname)
 #endif
 	int namespace_enabled = 0;
 	int mount_enabled = 0;
+	int tmp_errno;
 	int error;
 	int ret;
 
@@ -1297,7 +1298,14 @@ int cgroup_config_load_config(const char *pathname)
 
 	return 0;
 err_grp:
+	/*
+	 * Save off the error that has already occurred.  The errno from
+	 * cgroup_config_destroy_groups() is secondary to the original error that was reported,
+	 * and thus can be discarded;
+	 */
+	tmp_errno = last_errno;
 	cgroup_config_destroy_groups();
+	last_errno = tmp_errno;
 err_mnt:
 	cgroup_config_unmount_controllers();
 	cgroup_free_config();