The code to fetch a 64-bit value from user space was entirely buggered,
and has been since the code was merged in early 2016 in commit
b2f680380ddf ("x86/mm/32: Add support for 64-bit __get_user() on 32-bit
kernels").

Happily the buggered routine is almost certainly entirely unused, since
the normal way to access user space memory is just with the non-inlined
"get_user()", and the inlined version didn't even historically exist.

The normal "get_user()" case is handled by external hand-written asm in
arch/x86/lib/getuser.S that doesn't have either of these issues.

There were two independent bugs in __get_user_asm_u64():

 - it still did the STAC/CLAC user space access marking, even though
   that is now done by the wrapper macros, see commit 11f1a4b9755f
   ("x86: reorganize SMAP handling in user space accesses").

   This didn't result in a semantic error, it just means that the
   inlined optimized version was hugely less efficient than the
   allegedly slower standard version, since the CLAC/STAC overhead is
   quite high on modern Intel CPU's.

 - the double register %eax/%edx was marked as an output, but the %eax
   part of it was touched early in the asm, and could thus clobber other
   inputs to the asm that gcc didn't expect it to touch.

   In particular, that meant that the generated code could look like
   this:

        mov    (%eax),%eax
        mov    0x4(%eax),%edx

   where the load of %edx obviously was _supposed_ to be from the 32-bit
   word that followed the source of %eax, but because %eax was
   overwritten by the first instruction, the source of %edx was
   basically random garbage.

The fixes are trivial: remove the extraneous STAC/CLAC entries, and mark
the 64-bit output as early-clobber to let gcc know that no inputs should
alias with the output register.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@kernel.org   # v4.8+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Al noticed that unsafe_put_user() had type problems, and fixed them in
commit a7cc722fff0b ("fix unsafe_put_user()"), which made me look more
at those functions.

It turns out that unsafe_get_user() had a type issue too: it limited the
largest size of the type it could handle to "unsigned long".  Which is
fine with the current users, but doesn't match our existing normal
get_user() semantics, which can also handle "u64" even when that does
not fit in a long.

While at it, also clean up the type cast in unsafe_put_user().  We
actually want to just make it an assignment to the expected type of the
pointer, because we actually do want warnings from types that don't
convert silently.  And it makes the code more readable by not having
that one very long and complex line.

[ This patch might become stable material if we ever end up back-porting
  any new users of the unsafe uaccess code, but as things stand now this
  doesn't matter for any current existing uses. ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull misc uaccess fixes from Al Viro:
 "Fix for unsafe_put_user() (no callers currently in mainline, but
  anyone starting to use it will step into that) + alpha osf_wait4()
  infoleak fix"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  osf_wait4(): fix infoleak
  fix unsafe_put_user()

failing sys_wait4() won't fill struct rusage...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

__put_user_size() relies upon its first argument having the same type as what
the second one points to; the only other user makes sure of that and
unsafe_put_user() should do the same.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull KVM fixes from Radim Krčmář:
 "ARM:
   - a fix for a build failure introduced in -rc1 when tracepoints are
     enabled on 32-bit ARM.

   - disable use of stack pointer protection in the hyp code which can
     cause panics.

   - a handful of VGIC fixes.

   - a fix to the init of the redistributors on GICv3 systems that
     prevented boot with kvmtool on GICv3 systems introduced in -rc1.

   - a number of race conditions fixed in our MMU handling code.

   - a fix for the guest being able to program the debug extensions for
     the host on the 32-bit side.

  PPC:
   - fixes for build failures with PR KVM configurations.

   - a fix for a host crash that can occur on POWER9 with radix guests.

  x86:
   - fixes for nested PML and nested EPT.

   - a fix for crashes caused by reserved bits in SSE MXCSR that could
     have been set by userspace.

   - an optimization of halt polling that fixes high CPU overhead.

   - fixes for four reports from Dan Carpenter's static checker.

   - a protection around code that shouldn't have been preemptible.

   - a fix for port IO emulation"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (27 commits)
  KVM: x86: prevent uninitialized variable warning in check_svme()
  KVM: x86/vPMU: fix undefined shift in intel_pmu_refresh()
  KVM: x86: zero base3 of unusable segments
  KVM: X86: Fix read out-of-bounds vulnerability in kvm pio emulation
  KVM: x86: Fix potential preemption when get the current kvmclock timestamp
  KVM: Silence underflow warning in avic_get_physical_id_entry()
  KVM: arm/arm64: Hold slots_lock when unregistering kvm io bus devices
  KVM: arm/arm64: Fix bug when registering redist iodevs
  KVM: x86: lower default for halt_poll_ns
  kvm: arm/arm64: Fix use after free of stage2 page table
  kvm: arm/arm64: Force reading uncached stage2 PGD
  KVM: nVMX: fix EPT permissions as reported in exit qualification
  KVM: VMX: Don't enable EPT A/D feature if EPT feature is disabled
  KVM: x86: Fix load damaged SSEx MXCSR register
  kvm: nVMX: off by one in vmx_write_pml_buffer()
  KVM: arm: rename pm_fake handler to trap_raz_wi
  KVM: arm: plug potential guest hardware debug leakage
  kvm: arm/arm64: Fix race in resetting stage2 PGD
  KVM: arm/arm64: vgic-v3: Use PREbits to infer the number of ICH_APxRn_EL2 registers
  KVM: arm/arm64: vgic-v3: Do not use Active+Pending state for a HW interrupt
  ...

Pull xen fixes from Juergen Gross:
 "Some fixes for the new Xen 9pfs frontend and some minor cleanups"

* tag 'for-linus-4.12b-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: make xen_flush_tlb_all() static
  xen: cleanup pvh leftovers from pv-only sources
  xen/9pfs: p9_trans_xen_init and p9_trans_xen_exit can be static
  xen/9pfs: fix return value check in xen_9pfs_front_probe()

Pull ARM SoC fixes from Olof Johansson:
 "We had a small batch of fixes before -rc1, but here is a larger one.
  It contains a backmerge of 4.12-rc1 since some of the downstream
  branches we merge had that as base; at the same time we already had
  merged contents before -rc1 and rebase wasn't the right solution.

  A mix of random smaller fixes and a few things worth pointing out:

   - We've started telling people to avoid cross-tree shared branches if
     all they're doing is picking up one or two DT-used constants from a
     shared include file, and instead to use the numeric values on first
     submission. Follow-up moving over to symbolic names are sent in
     right after -rc1, i.e. here. It's only a few minor patches of this
     type.

   - Linus Walleij and others are resurrecting the 'Gemini' platform,
     and wanted a cut-down platform-specific defconfig for it. So I
     picked that up for them.

   - Rob Herring ran 'savedefconfig' on arm64, it's a bit churny but it
     helps people to prepare patches since it's a pain when defconfig
     and current savedefconfig contents differs too much.

   - Devicetree additions for some pinctrl drivers for Armada that were
     merged this window. I'd have preferred to see those earlier but
     it's not a huge deail.

  The biggest change worth pointing out though since it's touching other
  parts of the tree: We added prefixes to be used when cross-including
  DT contents between arm64 and arm, allowing someone to #include
  <arm/foo.dtsi> from arm64, and likewise. As part of that, we needed
  arm/foo.dtsi to work on arm as well. The way I suggested this to Heiko
  resulted in a recursive symlink.

  Instead, I've now moved it out of arch/*/boot/dts/include, into a
  shared location under scripts/dtc. While I was at it, I consolidated
  so all architectures now behave the same way in this manner.

  Rob Herring (DT maintainer) has acked it. I cc:d most other arch
  maintainers but nobody seems to care much; it doesn't really affect
  them since functionality is unchanged for them by default"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (29 commits)
  arm64: dts: rockchip: fix include reference
  firmware: ti_sci: fix strncat length check
  ARM: remove duplicate 'const' annotations'
  arm64: defconfig: enable options needed for QCom DB410c board
  arm64: defconfig: sync with savedefconfig
  ARM: configs: add a gemini defconfig
  devicetree: Move include prefixes from arch to separate directory
  ARM: dts: dra7: Reduce cpu thermal shutdown temperature
  memory: omap-gpmc: Fix debug output for access width
  ARM: dts: LogicPD Torpedo: Fix camera pin mux
  ARM: dts: omap4: enable CEC pin for Pandaboard A4 and ES
  ARM: dts: gta04: fix polarity of clocks for mcbsp4
  ARM: dts: dra7: Add power hold and power controller properties to palmas
  soc: imx: add PM dependency for IMX7_PM_DOMAINS
  ARM: dts: imx6sx-sdb: Remove OPP override
  ARM: dts: imx53-qsrb: Pulldown PMIC IRQ pin
  soc: bcm: brcmstb: Correctly match 7435 SoC
  tee: add ARM_SMCCC dependency
  ARM: omap2+: make omap4_get_cpu1_ns_pa_addr declaration usable
  ARM64: dts: mediatek: configure some fixed mmc parameters
  ...

Pull arm64 fixes/cleanups from Catalin Marinas:

 - Avoid taking a mutex in the secondary CPU bring-up path when
   interrupts are disabled

 - Ignore perf exclude_hv when the kernel is running in Hyp mode

 - Remove redundant instruction in cmpxchg

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64/cpufeature: don't use mutex in bringup path
  arm64: perf: Ignore exclude_hv when kernel is running in HYP
  arm64: Remove redundant mov from LL/SC cmpxchg

Pull powerpc fixes from Michael Ellerman:
 "The headliner is a fix for FP/VMX register corruption when using
  transactional memory, and a new selftest to go with it.

  Then there's the virt_addr_valid() fix, currently HARDENDED_USERCOPY
  is tripping on that causing some machines to crash.

  A few other fairly minor fixes for long tail things, and a couple of
  fixes for code we just merged.

  Thanks to: Breno Leitao, Gautham Shenoy, Michael Neuling, Naveen Rao.
  Nicholas Piggin, Paul Mackerras"

* tag 'powerpc-4.12-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/mm: Fix virt_addr_valid() etc. on 64-bit hash
  powerpc/mm: Fix crash in page table dump with huge pages
  powerpc/kprobes: Fix handling of instruction emulation on probe re-entry
  powerpc/powernv: Set NAPSTATELOST after recovering paca on P9 DD1
  selftests/powerpc: Test TM and VMX register state
  powerpc/tm: Fix FP and VMX register corruption
  powerpc/modules: If mprofile-kernel is enabled add it to vermagic