On Thu, May 10, 2018 at 05:34:13PM +0800, Xin Long wrote:
> In Commit 1f45f78f8e51 ("sctp: allow GSO frags to access the chunk too"),
> it held the chunk in sctp_ulpevent_make_rcvmsg to access it safely later
> in recvmsg. However, it also added sctp_chunk_put in fail_mark err path,
> which is only triggered before holding the chunk.
>
> syzbot reported a use-after-free crash happened on this err path, where
> it shouldn't call sctp_chunk_put.
>
> This patch simply removes this call.
>
> Fixes: 1f45f78f8e51 ("sctp: allow GSO frags to access the chunk too")
> Reported-by: syzbot+141d898c5f24489db4aa@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> net/sctp/ulpevent.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/net/sctp/ulpevent.c b/net/sctp/ulpevent.c
> index 84207ad..8cb7d98 100644
> --- a/net/sctp/ulpevent.c
> +++ b/net/sctp/ulpevent.c
> @@ -715,7 +715,6 @@ struct sctp_ulpevent *sctp_ulpevent_make_rcvmsg(struct sctp_association *asoc,
> return event;
>
> fail_mark:
> - sctp_chunk_put(chunk);
> kfree_skb(skb);
> fail:
> return NULL;
> --
> 2.1.0
>
>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
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