Re: [PATCH] cgroup: fix cgroup_get_from_id

[Mukesh Ojha <quic_mojha@quicinc.com>]

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