Messages in this thread | | | Date | Wed, 5 Apr 2017 09:44:15 -0300 | From | Marcelo Ricardo Leitner <> | Subject | Re: net/sctp: list double add warning in sctp_endpoint_add_asoc |
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On Wed, Apr 05, 2017 at 06:48:45PM +0800, Xin Long wrote: > On Wed, Apr 5, 2017 at 5:14 AM, Marcelo Ricardo Leitner > <marcelo.leitner@gmail.com> wrote: > > On Wed, Apr 05, 2017 at 01:29:19AM +0800, Xin Long wrote: > >> On Tue, Apr 4, 2017 at 9:28 PM, Andrey Konovalov <andreyknvl@google.com> wrote: > >> > Hi, > >> > > >> > I've got the following error report while fuzzing the kernel with syzkaller. > >> > > >> > On commit a71c9a1c779f2499fb2afc0553e543f18aff6edf (4.11-rc5). > >> > > >> > A reproducer and .config are attached. > >> The script is pretty hard to reproduce the issue in my env. > > > > I didn't try running it but I also found the reproducer very complicated > > to follow. Do you have any plans on having some PoC optimizer, so we can > > have a more readable code? > > strace is handy for filtering the noise, yes, but sometimes it doesn't > > cut it. > I got the script now: > 1. create sk > 2. set sk->sndbuf = x > 3. sendmsg with size s1 (s1 < x) > 4. sendmsg with size s2 (s1+s2 > x) > 5. sendmsg with size s3 (wspace < 0), wait sndbuf, schedule out. > 6. listen sk (abnormal operation on sctp client) > 7. accept sk. > > In step 6, sk->sk_state = listening, then step 7 could get the first asoc > from ep->asoc_list and alloc a new sk2, attach the asoc to sk2. > > after a while, sendmsg schedule in, but asoc->sk is sk2, !=sk. > the same issue we fix for peeloff on commit dfcb9f4f99f1 ("sctp: deny > peeloff operation on asocs with threads sleeping on it") happens.
Yes. That explains why the asoc isn't dead by when sendmsg comes back, and avoid that dead check.
> > But we should not fix it by the same way as for peeloff. the real reason > causes this issue is on step 6, it should disallow listen on the established sk.
Agreed.
> > The following fix should work for this, just similar with what > inet_listen() did. > > @@ -7174,6 +7175,9 @@ int sctp_inet_listen(struct socket *sock, int backlog) > if (sock->state != SS_UNCONNECTED) > goto out; > > + if (!sctp_sstate(sk, LISTENING) && !sctp_sstate(sk,CLOSED)) > + goto out; > + > > what do you think ?
Yes, agreed. Thanks!
Marcelo
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