On Tue, Jan 02, 2018 at 07:44:37PM -0200, Marcelo Ricardo Leitner wrote:
> syzbot noticed a NULL pointer dereference panic in sctp_stream_free()
> which was caused by an incomplete error handling in sctp_stream_init().
> By not clearing stream->outcnt, it made a for() in sctp_stream_free()
> think that it had elements to free, but not, leading to the panic.
>
> As suggested by Xin Long, this patch also simplifies the error path by
> moving it to the only if() that uses it.
>
> See-also: https://www.spinics.net/lists/netdev/msg473756.html
> See-also: https://www.spinics.net/lists/netdev/msg465024.html
> Reported-by: syzbot <syzkal...@googlegroups.com>
> Fixes: f952be79cebd ("sctp: introduce struct sctp_stream_out_ext")
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
> ---
> net/sctp/stream.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index
> 76ea66be0bbee7d3f018676d52c8b95ba06dbcb1..524dfeb94c41ab1ac735746a8acf93af1c96ae48
> 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -156,9 +156,9 @@ int sctp_stream_init(struct sctp_stream *stream, __u16
> outcnt, __u16 incnt,
> sctp_stream_outq_migrate(stream, NULL, outcnt);
> sched->sched_all(stream);
>
> - i = sctp_stream_alloc_out(stream, outcnt, gfp);
> - if (i)
> - return i;
> + ret = sctp_stream_alloc_out(stream, outcnt, gfp);
> + if (ret)
> + goto out;
>
> stream->outcnt = outcnt;
> for (i = 0; i < stream->outcnt; i++)
> @@ -170,19 +170,17 @@ int sctp_stream_init(struct sctp_stream *stream, __u16
> outcnt, __u16 incnt,
> if (!incnt)
> goto out;
>
> - i = sctp_stream_alloc_in(stream, incnt, gfp);
> - if (i) {
> - ret = -ENOMEM;
> - goto free;
> + ret = sctp_stream_alloc_in(stream, incnt, gfp);
> + if (ret) {
> + sched->free(stream);
> + kfree(stream->out);
> + stream->out = NULL;
> + stream->outcnt = 0;
> + goto out;
> }
>
> stream->incnt = incnt;
> - goto out;
>
> -free:
> - sched->free(stream);
> - kfree(stream->out);
> - stream->out = NULL;
> out:
> return ret;
> }
> --
> 2.14.3
>
>
Acked-by: Neil Horman <nhor...@tuxdriver.com>
