Messages in this thread Patch in this message | | | Date | Tue, 17 Mar 2020 01:15:23 -0300 | From | Marcelo Ricardo Leitner <> | Subject | Re: [PATCH] sctp: fix refcount bug in sctp_wfree |
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On Mon, Mar 16, 2020 at 11:53:24AM +0800, Qiujun Huang wrote: > Do accounting for skb's real sk. > In some case skb->sk != asoc->base.sk.
This is a too simple description. Please elaborate how this can happen in sctp_wfree. Especially considering the construct for migrating the tx queue on sctp_sock_migrate(), as both sockets are locked while moving the chunks around and the asoc itself is only moved in between decrementing and incrementing the refcount:
lock_sock_nested(newsk, SINGLE_DEPTH_NESTING); sctp_for_each_tx_datachunk(assoc, sctp_clear_owner_w); sctp_assoc_migrate(assoc, newsk); sctp_for_each_tx_datachunk(assoc, sctp_set_owner_w); ...
> > Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@syzkaller.appspotmail.com
I can't see a positive test result, though. If I didn't loose any email, your last test with a patch similar to this one actually failed. I'm talking about syzbot test result at Message-ID: <000000000000e7736205a0e041f5@google.com>
> Signed-off-by: Qiujun Huang <hqjagain@gmail.com> > --- > net/sctp/socket.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/net/sctp/socket.c b/net/sctp/socket.c > index 1b56fc4..5f5c28b 100644 > --- a/net/sctp/socket.c > +++ b/net/sctp/socket.c > @@ -9080,7 +9080,7 @@ static void sctp_wfree(struct sk_buff *skb) > { > struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg; > struct sctp_association *asoc = chunk->asoc; > - struct sock *sk = asoc->base.sk; > + struct sock *sk = skb->sk; > > sk_mem_uncharge(sk, skb->truesize); > sk->sk_wmem_queued -= skb->truesize + sizeof(struct sctp_chunk); > @@ -9109,7 +9109,7 @@ static void sctp_wfree(struct sk_buff *skb) > } > > sock_wfree(skb); > - sctp_wake_up_waiters(sk, asoc); > + sctp_wake_up_waiters(asoc->base.sk, asoc); > > sctp_association_put(asoc); > } > -- > 1.8.3.1 >
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