Pull namespace bugfixes from Eric Biederman:
 "This is three simple fixes against 3.9-rc1.  I have tested each of
  these fixes and verified they work correctly.

  The userns oops in key_change_session_keyring and the BUG_ON triggered
  by proc_ns_follow_link were found by Dave Jones.

  I am including the enhancement for mount to only trigger requests of
  filesystem modules here instead of delaying this for the 3.10 merge
  window because it is both trivial and the kind of change that tends to
  bit-rot if left untouched for two months."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  proc: Use nd_jump_link in proc_ns_follow_link
  fs: Limit sys_mount to only request filesystem modules (Part 2).
  fs: Limit sys_mount to only request filesystem modules.
  userns: Stop oopsing in key_change_session_keyring

We support DSCR (Data Stream Control Register) so we should make sure we set it
in the FSCR (Facility Status & Control Register) incase some firmwares don't
set it.  If we don't set this, we'll take a facility unavailable exception when
using the DSCR.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

This sets the DSCR (Data Stream Control Register) in the FSCR (Facility Status
& Control Register).

Also harmonise TAR (Target Address Register) FSCR bit definition too.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Currently we only set the FSCR (Facility Status and Control Register) when HV=1
but this feature is available when HV=0 also.  This patch sets FSCR when HV=0.

Also, we currently only set the FSCR on the master CPU.  This patch also sets
the FSCR on secondary CPUs.

Signed-off-by: Michael Neuling <mikey@neuling.org>
cc: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Since kmp takes 2 unsigned long args there should be a compat wrapper.
Since one isn't provided I think it's safer just to hook this up to not
implemented.  If we need it later we can do it properly then.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

The BITOP_LE_SWIZZLE macro was used in the little-endian bitops functions
for powerpc.  But these functions were converted to generic bitops and
the BITOP_LE_SWIZZLE is not used anymore.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Currently we use the link register to branch up high in the early MMU on
syscall entry path.  Unfortunately, this trashes the link stack as the
address we are going to is not associated with the earlier mflr.

This patch simply converts us to used the count register (volatile over
syscalls anyway) instead.  This is much better at predicting in this
scenario and doesn't trash link stack causing a bunch of additional
branch mispredicts later.  Benchmarking this on POWER8 saves a bunch of
cycles on Anton's null syscall benchmark here:
   http://ozlabs.org/~anton/junkcode/null_syscall.c

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

the dest buf len is 80 (HVCS_CLC_LENGTH + 1).
  the src buf len is PAGE_SIZE.
  if src buf string len is more than 80, it will cause issue.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

When building with CRYPTO_SHA1_PPC enabled we fail with:

powerpc/crypto/sha1-powerpc-asm.S: Assembler messages:
powerpc/crypto/sha1-powerpc-asm.S:116: Error: can't resolve `0' {*ABS* section} - `STACKFRAMESIZE' {*UND* section}
powerpc/crypto/sha1-powerpc-asm.S:116: Error: expression too complex
powerpc/crypto/sha1-powerpc-asm.S:178: Error: unsupported relocation against STACKFRAMESIZE

Use INT_FRAME_SIZE instead of STACKFRAMESIZE.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Tested-by: Christian Kujau <lists@nerdbynature.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives.  Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work.  While writing this patch I saw a handful of such
cases.  The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module.  The common pattern in the kernel is to call request_module()
without regards to the users permissions.  In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted.  In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>