[PATCH 3.2 005/102] cgroup: reject cgroup names with '\n'

[Ben Hutchings]

3.2.64-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Alban Crequy <alban.crequy@xxxxxxxxxxxxxxx>

commit 71b1fb5c4473a5b1e601d41b109bdfe001ec82e0 upstream.

/proc/<pid>/cgroup contains one cgroup path on each line. If cgroup names are
allowed to contain "\n", applications cannot parse /proc/<pid>/cgroup safely.

Signed-off-by: Alban Crequy <alban.crequy@xxxxxxxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
[bwh: Backported to 3.2:
 - Adjust context
 - We have to get the name from the dentry pointer]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/cgroup.c | 5 +++++
 1 file changed, 5 insertions(+)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3871,6 +3871,11 @@ static int cgroup_mkdir(struct inode *di
 {
 	struct cgroup *c_parent = dentry->d_parent->d_fsdata;
 
+	/* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
+	 */
+	if (strchr(dentry->d_name.name, '\n'))
+		return -EINVAL;
+
 	/* the vfs holds inode->i_mutex already */
 	return cgroup_create(c_parent, dentry, mode | S_IFDIR);
 }

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