1. 11 Jul, 2016 9 commits
  2. 09 Jul, 2016 1 commit
    • Rainer Weikusat's avatar
      af_unix: Fix splice-bind deadlock · 272d474f
      Rainer Weikusat authored
      [ Upstream commit c845acb3 ]
      
      On 2015/11/06, Dmitry Vyukov reported a deadlock involving the splice
      system call and AF_UNIX sockets,
      
      http://lists.openwall.net/netdev/2015/11/06/24
      
      The situation was analyzed as
      
      (a while ago) A: socketpair()
      B: splice() from a pipe to /mnt/regular_file
      	does sb_start_write() on /mnt
      C: try to freeze /mnt
      	wait for B to finish with /mnt
      A: bind() try to bind our socket to /mnt/new_socket_name
      	lock our socket, see it not bound yet
      	decide that it needs to create something in /mnt
      	try to do sb_start_write() on /mnt, block (it's
      	waiting for C).
      D: splice() from the same pipe to our socket
      	lock the pipe, see that socket is connected
      	try to lock the socket, block waiting for A
      B:	get around to actually feeding a chunk from
      	pipe to file, try to lock the pipe.  Deadlock.
      
      on 2015/11/10 by Al Viro,
      
      http://lists.openwall.net/netdev/2015/11/10/4
      
      The patch fixes this by removing the kern_path_create related code from
      unix_mknod and executing it as part of unix_bind prior acquiring the
      readlock of the socket in question. This means that A (as used above)
      will sb_start_write on /mnt before it acquires the readlock, hence, it
      won't indirectly block B which first did a sb_start_write and then
      waited for a thread trying to acquire the readlock. Consequently, A
      being blocked by C waiting for B won't cause a deadlock anymore
      (effectively, both A and B acquire two locks in opposite order in the
      situation described above).
      
      Dmitry Vyukov(<dvyukov@google.com>) tested the original patch.
      Signed-off-by: default avatarRainer Weikusat <rweikusat@mobileactivedefense.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
      272d474f
  3. 23 Jun, 2016 1 commit
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  5. 17 Jun, 2016 16 commits