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@xxxxxxxxxxxxxxxxxxxxxxxxx
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@xxxxxxxxxx>
> Signed-off-by: Qiujun Huang <hqjagain@xxxxxxxxx>
> ---
> 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
>
