On Thu, Jun 27, 2019 at 07:48:10PM -0300, Marcelo Ricardo Leitner wrote:
> It allocates the extended area for outbound streams only on sendmsg
> calls, if they are not yet allocated. When using the priority
> stream scheduler, this initialization may imply into a subsequent
> allocation, which may fail. In this case, it was aborting the stream
> scheduler initialization but leaving the ->ext pointer (allocated) in
> there, thus in a partially initialized state. On a subsequent call to
> sendmsg, it would notice the ->ext pointer in there, and trip on
> uninitialized stuff when trying to schedule the data chunk.
>
> The fix is undo the ->ext initialization if the stream scheduler
> initialization fails and avoid the partially initialized state.
>
> Although syzkaller bisected this to commit 4ff40b86262b ("sctp: set
> chunk transport correctly when it's a new asoc"), this bug was actually
> introduced on the commit I marked below.
>
> Reported-by: syzbot+c1a380d42b190ad1e559@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
> Tested-by: Xin Long <lucien.xin@xxxxxxxxx>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> ---
> net/sctp/stream.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index 93ed07877337eace4ef7f4775dda5868359ada37..25946604af85c09917e63e5c4a8d7d6fa2caebc4 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -153,13 +153,20 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
> int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
> {
> struct sctp_stream_out_ext *soute;
> + int ret;
>
> soute = kzalloc(sizeof(*soute), GFP_KERNEL);
> if (!soute)
> return -ENOMEM;
> SCTP_SO(stream, sid)->ext = soute;
>
> - return sctp_sched_init_sid(stream, sid, GFP_KERNEL);
> + ret = sctp_sched_init_sid(stream, sid, GFP_KERNEL);
> + if (ret) {
> + kfree(SCTP_SO(stream, sid)->ext);
> + SCTP_SO(stream, sid)->ext = NULL;
> + }
> +
> + return ret;
> }
>
> void sctp_stream_free(struct sctp_stream *stream)
> --
> 2.21.0
>
>
Acked-by: Neil Horman <nhorman@xxxxxxxxxx>
