1. 15 Dec, 2015 1 commit
    • Hannes Frederic Sowa's avatar
      af-unix: fix use-after-free with concurrent readers while splicing · 44fc75be
      Hannes Frederic Sowa authored
      [ Upstream commit 73ed5d25 ]
      
      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: 2b514574 ("net: af_unix: implement splice for stream af_unix sockets")
      Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
      Cc: Dmitry Vyukov <dvyukov@google.com>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Acked-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      44fc75be
  2. 09 Dec, 2015 39 commits