This is a note to let you know that I've just added the patch titled cgroup1: don't allow '\n' in renaming to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cgroup1-don-t-allow-n-in-renaming.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b7e24eb1caa5f8da20d405d262dba67943aedc42 Mon Sep 17 00:00:00 2001 From: Alexander Kuznetsov <wwfq@xxxxxxxxxxxxxx> Date: Wed, 9 Jun 2021 10:17:19 +0300 Subject: cgroup1: don't allow '\n' in renaming From: Alexander Kuznetsov <wwfq@xxxxxxxxxxxxxx> commit b7e24eb1caa5f8da20d405d262dba67943aedc42 upstream. cgroup_mkdir() have restriction on newline usage in names: $ mkdir $'/sys/fs/cgroup/cpu/test\ntest2' mkdir: cannot create directory '/sys/fs/cgroup/cpu/test\ntest2': Invalid argument But in cgroup1_rename() such check is missed. This allows us to make /proc/<pid>/cgroup unparsable: $ mkdir /sys/fs/cgroup/cpu/test $ mv /sys/fs/cgroup/cpu/test $'/sys/fs/cgroup/cpu/test\ntest2' $ echo $$ > $'/sys/fs/cgroup/cpu/test\ntest2' $ cat /proc/self/cgroup 11:pids:/ 10:freezer:/ 9:hugetlb:/ 8:cpuset:/ 7:blkio:/user.slice 6:memory:/user.slice 5:net_cls,net_prio:/ 4:perf_event:/ 3:devices:/user.slice 2:cpu,cpuacct:/test test2 1:name=systemd:/ 0::/ Signed-off-by: Alexander Kuznetsov <wwfq@xxxxxxxxxxxxxx> Reported-by: Andrey Krasichkov <buglloc@xxxxxxxxxxxxxx> Acked-by: Dmitry Yakunin <zeil@xxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/cgroup/cgroup-v1.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -820,6 +820,10 @@ static int cgroup1_rename(struct kernfs_ struct cgroup *cgrp = kn->priv; int ret; + /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */ + if (strchr(new_name_str, '\n')) + return -EINVAL; + if (kernfs_type(kn) != KERNFS_DIR) return -ENOTDIR; if (kn->parent != new_parent) Patches currently in stable-queue which might be from wwfq@xxxxxxxxxxxxxx are queue-5.12/cgroup1-don-t-allow-n-in-renaming.patch