1. 17 Nov, 2014 39 commits
  2. 14 Nov, 2014 1 commit
    • Al Viro's avatar
      fix misuses of f_count() in ppp and netlink · a0649e6d
      Al Viro authored
      commit 24dff96a upstream.
      
      we used to check for "nobody else could start doing anything with
      that opened file" by checking that refcount was 2 or less - one
      for descriptor table and one we'd acquired in fget() on the way to
      wherever we are.  That was race-prone (somebody else might have
      had a reference to descriptor table and do fget() just as we'd
      been checking) and it had become flat-out incorrect back when
      we switched to fget_light() on those codepaths - unlike fget(),
      it doesn't grab an extra reference unless the descriptor table
      is shared.  The same change allowed a race-free check, though -
      we are safe exactly when refcount is less than 2.
      
      It was a long time ago; pre-2.6.12 for ioctl() (the codepath leading
      to ppp one) and 2.6.17 for sendmsg() (netlink one).  OTOH,
      netlink hadn't grown that check until 3.9 and ppp used to live
      in drivers/net, not drivers/net/ppp until 3.1.  The bug existed
      well before that, though, and the same fix used to apply in old
      location of file.
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
      a0649e6d