Re: [PATCH net v2] sctp: fix a potential buffer overflow in sctp_sched_set_sched()

[Xin Long]

On Tue, May 2, 2023 at 9:03 AM Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx> wrote:
>
> The 'sched' index value must be checked before accessing an element
> of the 'sctp_sched_ops' array. Otherwise, it can lead to buffer overflow.
>
> Note that it's harmless since the 'sched' parameter is checked before
> calling 'sctp_sched_set_sched'.
>
> Found by InfoTeCS on behalf of Linux Verification Center
> (linuxtesting.org) with SVACE.
>
> Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
> Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
> Signed-off-by: Ilia.Gavrilov <Ilia.Gavrilov@xxxxxxxxxxx>
> ---
> V2:
>  - Change the order of local variables
>  - Specify the target tree in the subject
>  net/sctp/stream_sched.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/net/sctp/stream_sched.c b/net/sctp/stream_sched.c
> index 330067002deb..4d076a9b8592 100644
> --- a/net/sctp/stream_sched.c
> +++ b/net/sctp/stream_sched.c
> @@ -146,18 +146,19 @@ static void sctp_sched_free_sched(struct sctp_stream *stream)
>  int sctp_sched_set_sched(struct sctp_association *asoc,
>                          enum sctp_sched_type sched)
>  {
> -       struct sctp_sched_ops *n = sctp_sched_ops[sched];
>         struct sctp_sched_ops *old = asoc->outqueue.sched;
>         struct sctp_datamsg *msg = NULL;
> +       struct sctp_sched_ops *n;
>         struct sctp_chunk *ch;
>         int i, ret = 0;
>
> -       if (old == n)
> -               return ret;
> -
>         if (sched > SCTP_SS_MAX)
>                 return -EINVAL;
>
> +       n = sctp_sched_ops[sched];
> +       if (old == n)
> +               return ret;
> +
>         if (old)
>                 sctp_sched_free_sched(&asoc->stream);
>
> --
> 2.30.2

Reviewed-by: Xin Long <lucien.xin@xxxxxxxxx>