Re: [PATCH] cgroup: fix cgroup_get_from_id

Mukesh Ojha
2022-09-23T15:43:15Z

Hi,

On 9/23/2022 5:21 PM, Ming Lei wrote:
> cgroup has to be one kernfs dir, otherwise kernel panic is caused,
> especially cgroup id is provide from userspace.
>
> Reported-by: Marco Patalano <mpatalan@redhat.com>
> Fixes: 6b658c4863c1 ("scsi: cgroup: Add cgroup_get_from_id()")
> Cc: Muneendra <muneendra.kumar@broadcom.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
> kernel/cgroup/cgroup.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index e4bb5d57f4d1..5f2090d051ac 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -6049,6 +6049,9 @@ struct cgroup *cgroup_get_from_id(u64 id)
> if (!kn)
> goto out;
>
> + if (kernfs_type(kn) != KERNFS_DIR)
> + goto put;
> +
> rcu_read_lock();
>
> cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
> @@ -6056,7 +6059,7 @@ struct cgroup *cgroup_get_from_id(u64 id)
> cgrp = NULL;
>
> rcu_read_unlock();
> -
> +put:
> kernfs_put(kn);
> out:
> return cgrp;

Good catch.

Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>

-Mukesh