Re: general protection fault in sctp_sched_prio_sched
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: 2019-06-17 13:49:20
Also in:
linux-sctp, lkml
Possibly related (same subject, not in this thread)
- 2019-06-18 · Re: general protection fault in sctp_sched_prio_sched · Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
- 2019-06-18 · Re: general protection fault in sctp_sched_prio_sched · Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
- 2019-06-15 · general protection fault in sctp_sched_prio_sched · syzbot <hidden>
Hi, On Sun, Jun 16, 2019 at 11:38:03PM +0800, Hillf Danton wrote:
Hello Syzbot On Sat, 15 Jun 2019 16:36:06 -0700 (PDT) syzbot wrote:quoted
Hello, syzbot found the following crash on:
...
quoted hunk
Check prio_head and bail out if it is not valid. Thanks Hillf ----->8--- --- net/sctp/stream_sched_prio.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/net/sctp/stream_sched_prio.c b/net/sctp/stream_sched_prio.c index 2245083..db25a43 100644 --- a/net/sctp/stream_sched_prio.c +++ b/net/sctp/stream_sched_prio.c@@ -135,6 +135,8 @@ static void sctp_sched_prio_sched(struct sctp_stream *stream,struct sctp_stream_priorities *prio, *prio_head; prio_head = soute->prio_head; + if (!prio_head) + return; /* Nothing to do if already scheduled */ if (!list_empty(&soute->prio_list)) --
Thanks but this is not a good fix for this. It will cause the stream
to never be scheduled.
The problem happens because of the fault injection that happened a bit
before the crash, in here:
int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
{
struct sctp_stream_out_ext *soute;
soute = kzalloc(sizeof(*soute), GFP_KERNEL);
if (!soute)
return -ENOMEM;
SCTP_SO(stream, sid)->ext = soute; <---- [A]
return sctp_sched_init_sid(stream, sid, GFP_KERNEL);
^^^^^^^^^^^^---- [B] failed
}
This causes the 1st sendmsg to bail out with the error. When the 2nd
one gets in, it will:
sctp_sendmsg_to_asoc()
{
...
if (unlikely(!SCTP_SO(&asoc->stream, sinfo->sinfo_stream)->ext)) {
^^^^^--- [C]
err = sctp_stream_init_ext(&asoc->stream, sinfo->sinfo_stream);
if (err)
goto err;
}
[A] leaves ext initialized, despite the failed in [B]. Then in [C], it
will not try to initialize again.
We need to either uninitialize ->ext as error handling for [B], or
improve the check on [C].
syzbot++ once again.
Marcelo