From: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
Date: Tue, 2 May 2023 13:03:24 +0000
> The 'sched' index value must be checked before accessing an element
> of the 'sctp_sched_ops' array. Otherwise, it can lead to buffer overflow.
OOB access ?
But it's not true because it does not happen in the first place.
>
> 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;
I'd just remove this check instead because the same test is done
in the caller side, sctp_setsockopt_scheduler(), and this errno
is never returned.
This unnecessary test confuses a reader like sched could be over
SCTP_SS_MAX here.
Since the OOB access does not happen, I think this patch should
go to net-next without the Fixes tag after the merge window.
Thanks,
Kuniyuki
>
> + n = sctp_sched_ops[sched];
> + if (old == n)
> + return ret;
> +
> if (old)
> sctp_sched_free_sched(&asoc->stream);
>
> --
> 2.30.2
