From: Hannes Frederic Sowa <han...@stressinduktion.org> Date: Tue, 10 Nov 2015 16:23:15 +0100
> During splicing an af-unix socket to a pipe we have to drop all > af-unix socket locks. While doing so we allow another reader to enter > unix_stream_read_generic which can read, copy and finally free another > skb. If exactly this skb is just in process of being spliced we get a > use-after-free report by kasan. > > First, we must make sure to not have a free while the skb is used during > the splice operation. We simply increment its use counter before unlocking > the reader lock. > > Stream sockets have the nice characteristic that we don't care about > zero length writes and they never reach the peer socket's queue. That > said, we can take the UNIXCB.consumed field as the indicator if the > skb was already freed from the socket's receive queue. If the skb was > fully consumed after we locked the reader side again we know it has been > dropped by a second reader. We indicate a short read to user space and > abort the current splice operation. > > This bug has been found with syzkaller > (http://github.com/google/syzkaller) by Dmitry Vyukov. > > Fixes: 2b514574f7e8 ("net: af_unix: implement splice for stream af_unix > sockets") > Reported-by: Dmitry Vyukov <dvyu...@google.com> > Cc: Dmitry Vyukov <dvyu...@google.com> > Cc: Eric Dumazet <eric.duma...@gmail.com> > Acked-by: Eric Dumazet <eduma...@google.com> > Signed-off-by: Hannes Frederic Sowa <han...@stressinduktion.org> Applied and queued up for -stable, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
