[PATCH] LSM: add missing hook to do_compat_readv_writev()

This patch addresses a flaw in LSM, where there is no mediation of readv()
and writev() in for 32-bit compatible apps using a 64-bit kernel.

This bug was discovered and fixed initially in the native readv/writev
code [1], but was not fixed in the compat code.  Thanks to Al for spotting
this one.

  [1] http://lwn.net/Articles/154282/

Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>