mm: simplify compat numa syscalls

The compat implementations for mbind, get_mempolicy, set_mempolicy and
migrate_pages are just there to handle the subtly different layout of
bitmaps on 32-bit hosts.

The compat implementation however lacks some of the checks that are
present in the native one, in particular for checking that the extra bits
are all zero when user space has a larger mask size than the kernel.
Worse, those extra bits do not get cleared when copying in or out of the
kernel, which can lead to incorrect data as well.

Unify the implementation to handle the compat bitmap layout directly in
the get_nodes() and copy_nodes_to_user() helpers.  Splitting out the
get_bitmap() helper from get_nodes() also helps readability of the native
case.

On x86, two additional problems are addressed by this: compat tasks can
pass a bitmap at the end of a mapping, causing a fault when reading across
the page boundary for a 64-bit word.  x32 tasks might also run into
problems with get_mempolicy corrupting data when an odd number of 32-bit
words gets passed.

On parisc the migrate_pages() system call apparently had the wrong calling
convention, as big-endian architectures expect the words inside of a
bitmap to be swapped.  This is not a problem though since parisc has no
NUMA support.

[[email protected]: fix mempolicy crash]
  Link: https://lkml.kernel.org/r/[email protected]
  Link: https://lore.kernel.org/lkml/YQPLG20V3dmOfq3a@osiris/

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Feng Tang <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions