cgroups: fix to return errno in a failure path

In cgroup_create(), if alloc_css_id() returns failure, the errno is not propagated to userspace, so mkdir will fail silently. To trigger this bug, we mount blkio (or memory subsystem), and create more then 65534 cgroups. (The number of cgroups is limited to 65535 if a subsystem has use_id == 1) # mount -t cgroup -o blkio xxx /mnt # for ((i = 0; i < 65534; i++)); do mkdir /mnt/$i; done # mkdir /mnt/65534 (should return ENOSPC) # Signed-off-by: Li Zefan <[email protected]> Acked-by: Serge Hallyn <[email protected]> Acked-by: Paul Menage <[email protected]> Acked-by: KAMEZAWA Hiroyuki <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
Baughn · Feb 3, 2010 · 4528fd0 · 4528fd0
1 parent ef2b9b0
commit 4528fd0
Showing 1 changed file with 5 additions and 2 deletions.
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
@@ -2936,14 +2936,17 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
 	for_each_subsys(root, ss) {
 		struct cgroup_subsys_state *css = ss->create(ss, cgrp);
+
 		if (IS_ERR(css)) {
 			err = PTR_ERR(css);
 			goto err_destroy;
 		}
 		init_cgroup_css(css, ss, cgrp);
-		if (ss->use_id)
-			if (alloc_css_id(ss, parent, cgrp))
+		if (ss->use_id) {
+			err = alloc_css_id(ss, parent, cgrp);
+			if (err)
 				goto err_destroy;
+		}
 		/* At error, ->destroy() callback has to free assigned ID. */
 	}