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SubjectRe: [PATCH net] sctp: set stream ext to NULL after freeing it in sctp_stream_outq_migrate
On Tue, Feb 12, 2019 at 06:51:01PM +0800, Xin Long wrote:
> In sctp_stream_init(), after sctp_stream_outq_migrate() freed the
> surplus streams' ext, but sctp_stream_alloc_out() returns -ENOMEM,
> stream->outcnt will not be set to 'outcnt'.
>
> With the bigger value on stream->outcnt, when closing the assoc and
> freeing its streams, the ext of those surplus streams will be freed
> again since those stream exts were not set to NULL after freeing in
> sctp_stream_outq_migrate(). Then the invalid-free issue reported by
> syzbot would be triggered.
>
> We fix it by simply setting them to NULL after freeing.
>
> Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
> Reported-by: syzbot+58e480e7b28f2d890bfd@syzkaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@gmail.com>
> ---
> net/sctp/stream.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index f246331..2936ed1 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -144,8 +144,10 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> }
> }
>
> - for (i = outcnt; i < stream->outcnt; i++)
> + for (i = outcnt; i < stream->outcnt; i++) {
> kfree(SCTP_SO(stream, i)->ext);
> + SCTP_SO(stream, i)->ext = NULL;
> + }
> }
>
> static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
> --
> 2.1.0
>
>
Acked-by: Neil Horman <nhorman@tuxdriver.com>

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