From: Marcelo Ricardo Leitner <[email protected]> commit 7233bc84a3aeda835d334499dc00448373caf5c0 upstream.
sctp_wait_for_connect() currently already holds the asoc to keep it alive during the sleep, in case another thread release it. But Andrey Konovalov and Dmitry Vyukov reported an use-after-free in such situation. Problem is that __sctp_connect() doesn't get a ref on the asoc and will do a read on the asoc after calling sctp_wait_for_connect(), but by then another thread may have closed it and the _put on sctp_wait_for_connect will actually release it, causing the use-after-free. Fix is, instead of doing the read after waiting for the connect, do it before so, and avoid this issue as the socket is still locked by then. There should be no issue on returning the asoc id in case of failure as the application shouldn't trust on that number in such situations anyway. This issue doesn't exist in sctp_sendmsg() path. Reported-by: Dmitry Vyukov <[email protected]> Reported-by: Andrey Konovalov <[email protected]> Tested-by: Andrey Konovalov <[email protected]> Signed-off-by: Marcelo Ricardo Leitner <[email protected]> Reviewed-by: Xin Long <[email protected]> Acked-by: Neil Horman <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Willy Tarreau <[email protected]> --- net/sctp/socket.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 86e7352..ede7c54 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -1231,9 +1231,12 @@ static int __sctp_connect(struct sock* sk, timeo = sock_sndtimeo(sk, f_flags & O_NONBLOCK); - err = sctp_wait_for_connect(asoc, &timeo); - if ((err == 0 || err == -EINPROGRESS) && assoc_id) + if (assoc_id) *assoc_id = asoc->assoc_id; + err = sctp_wait_for_connect(asoc, &timeo); + /* Note: the asoc may be freed after the return of + * sctp_wait_for_connect. + */ /* Don't free association on exit. */ asoc = NULL; -- 2.8.0.rc2.1.gbe9624a
