cgroup: don't put ERR_PTR() into fc->root

Al Viro · Al Viro · commit 630faf81b3e6 · 2019-11-10T11:53:27.000-05:00
the caller of -&gt;get_tree() expects NULL left there on error...

Reported-by: Thibaut Sautereau &lt;thibaut@sautereau.fr&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
@@ -2119,11 +2119,12 @@ int cgroup_do_get_tree(struct fs_context *fc)
 
 		nsdentry = kernfs_node_dentry(cgrp->kn, sb);
 		dput(fc->root);
-		fc->root = nsdentry;
 		if (IS_ERR(nsdentry)) {
-			ret = PTR_ERR(nsdentry);
 			deactivate_locked_super(sb);
+			ret = PTR_ERR(nsdentry);
+			nsdentry = NULL;
 		}
+		fc->root = nsdentry;
 	}
 
 	if (!ctx->kfc.new_sb_created)

Original file line number	Diff line number	Diff line change
`@@ -2119,11 +2119,12 @@ int cgroup_do_get_tree(struct fs_context *fc)`
`2119`	`2119`
`2120`	`2120`	`nsdentry = kernfs_node_dentry(cgrp->kn, sb);`
`2121`	`2121`	`dput(fc->root);`
`2122`		`- fc->root = nsdentry;`
`2123`	`2122`	`if (IS_ERR(nsdentry)) {`
`2124`		`- ret = PTR_ERR(nsdentry);`
`2125`	`2123`	`deactivate_locked_super(sb);`
	`2124`	`+ ret = PTR_ERR(nsdentry);`
	`2125`	`+ nsdentry = NULL;`
`2126`	`2126`	`}`
	`2127`	`+ fc->root = nsdentry;`
`2127`	`2128`	`}`
`2128`	`2129`
`2129`	`2130`	`if (!ctx->kfc.new_sb_created)`