linux-stable.git/arch/x86/kernel/fpu, branch linux-4.9.y

x86/fpu: Make init_fpstate correct with optimized XSAVE

2021-08-26T12:37:25+00:00

commit f9dfb5e390fab2df9f7944bb91e7705aba14cd26 upstream.

The XSAVE init code initializes all enabled and supported components with
XRSTOR(S) to init state. Then it XSAVEs the state of the components back
into init_fpstate which is used in several places to fill in the init state
of components.

This works correctly with XSAVE, but not with XSAVEOPT and XSAVES because
those use the init optimization and skip writing state of components which
are in init state. So init_fpstate.xsave still contains all zeroes after
this operation.

There are two ways to solve that:

   1) Use XSAVE unconditionally, but that requires to reshuffle the buffer when
      XSAVES is enabled because XSAVES uses compacted format.

   2) Save the components which are known to have a non-zero init state by other
      means.

Looking deeper, #2 is the right thing to do because all components the
kernel supports have all-zeroes init state except the legacy features (FP,
SSE). Those cannot be hard coded because the states are not identical on all
CPUs, but they can be saved with FXSAVE which avoids all conditionals.

Use FXSAVE to save the legacy FP/SSE components in init_fpstate along with
a BUILD_BUG_ON() which reminds developers to validate that a newly added
component has all zeroes init state. As a bonus remove the now unused
copy_xregs_to_kernel_booting() crutch.

The XSAVE and reshuffle method can still be implemented in the unlikely
case that components are added which have a non-zero init state and no
other means to save them. For now, FXSAVE is just simple and good enough.

  [ bp: Fix a typo or two in the text. ]

Fixes: 6bad06b76892 ("x86, xsave: Use xsaveopt in context-switch path when supported")
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Reviewed-by: Borislav Petkov 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210618143444.587311343@linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/fpu: Limit xstate copy size in xstateregs_set()

2021-07-20T14:21:14+00:00

[ Upstream commit 07d6688b22e09be465652cf2da0da6bf86154df6 ]

If the count argument is larger than the xstate size, this will happily
copy beyond the end of xstate.

Fixes: 91c3dba7dbc1 ("x86/fpu/xstate: Fix PTRACE frames for XSAVES")
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Reviewed-by: Andy Lutomirski 
Reviewed-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121452.120741557@linutronix.de
Signed-off-by: Sasha Levin

x86/fpu: Reset state for all signal restore failures

2021-06-30T12:49:18+00:00

commit efa165504943f2128d50f63de0c02faf6dcceb0d upstream.

If access_ok() or fpregs_soft_set() fails in __fpu__restore_sig() then the
function just returns but does not clear the FPU state as it does for all
other fatal failures.

Clear the FPU state for these failures as well.

Fixes: 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman

x86/pkeys: Add check for pkey "overflow"

2020-10-01T18:40:08+00:00

[ Upstream commit 16171bffc829272d5e6014bad48f680cb50943d9 ]

Alex Shi reported the pkey macros above arch_set_user_pkey_access()
to be unused.  They are unused, and even refer to a nonexistent
CONFIG option.

But, they might have served a good use, which was to ensure that
the code does not try to set values that would not fit in the
PKRU register.  As it stands, a too-large 'pkey' value would
be likely to silently overflow the u32 new_pkru_bits.

Add a check to look for overflows.  Also add a comment to remind
any future developer to closely examine the types used to store
pkey values if arch_max_pkey() ever changes.

This boots and passes the x86 pkey selftests.

Reported-by: Alex Shi 
Signed-off-by: Dave Hansen 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20200122165346.AD4DA150@viggo.jf.intel.com
Signed-off-by: Sasha Levin

x86/fpu: Disable bottom halves while loading FPU registers

2018-12-29T12:40:15+00:00

commit 68239654acafe6aad5a3c1dc7237e60accfebc03 upstream.

The sequence

  fpu->initialized = 1;		/* step A */
  preempt_disable();		/* step B */
  fpu__restore(fpu);
  preempt_enable();

in __fpu__restore_sig() is racy in regard to a context switch.

For 32bit frames, __fpu__restore_sig() prepares the FPU state within
fpu->state. To ensure that a context switch (switch_fpu_prepare() in
particular) does not modify fpu->state it uses fpu__drop() which sets
fpu->initialized to 0.

After fpu->initialized is cleared, the CPU's FPU state is not saved
to fpu->state during a context switch. The new state is loaded via
fpu__restore(). It gets loaded into fpu->state from userland and
ensured it is sane. fpu->initialized is then set to 1 in order to avoid
fpu__initialize() doing anything (overwrite the new state) which is part
of fpu__restore().

A context switch between step A and B above would save CPU's current FPU
registers to fpu->state and overwrite the newly prepared state. This
looks like a tiny race window but the Kernel Test Robot reported this
back in 2016 while we had lazy FPU support. Borislav Petkov made the
link between that report and another patch that has been posted. Since
the removal of the lazy FPU support, this race goes unnoticed because
the warning has been removed.

Disable bottom halves around the restore sequence to avoid the race. BH
need to be disabled because BH is allowed to run (even with preemption
disabled) and might invoke kernel_fpu_begin() by doing IPsec.

 [ bp: massage commit message a bit. ]

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Borislav Petkov 
Acked-by: Ingo Molnar 
Acked-by: Thomas Gleixner 
Cc: Andy Lutomirski 
Cc: Dave Hansen 
Cc: "H. Peter Anvin" 
Cc: "Jason A. Donenfeld" 
Cc: kvm ML 
Cc: Paolo Bonzini 
Cc: Radim Krčmář 
Cc: Rik van Riel 
Cc: stable@vger.kernel.org
Cc: x86-ml 
Link: http://lkml.kernel.org/r/20181120102635.ddv3fvavxajjlfqk@linutronix.de
Link: https://lkml.kernel.org/r/20160226074940.GA28911@pd.tnic
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Greg Kroah-Hartman

x86/fpu: Remove second definition of fpu in fpurestore_sig()

2018-11-13T19:16:48+00:00

[ Upstream commit 6aa676761d4c1acfa31320e55fa1f83f3fcbbc7a ]

Commit:

  c5bedc6847c3b ("x86/fpu: Get rid of PF_USED_MATH usage, convert it to fpu->fpstate_active")

introduced the 'fpu' variable at top of __restore_xstate_sig(),
which now shadows the other definition:

  arch/x86/kernel/fpu/signal.c:318:28: warning: symbol 'fpu' shadows an earlier one
  arch/x86/kernel/fpu/signal.c:271:20: originally declared here

Remove the shadowed definition of 'fpu', as the two definitions are the same.

Signed-off-by: Sebastian Andrzej Siewior 
Reviewed-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Dave Hansen 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Fixes: c5bedc6847c3b ("x86/fpu: Get rid of PF_USED_MATH usage, convert it to fpu->fpstate_active")
Link: http://lkml.kernel.org/r/20181016202525.29437-3-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

x86/fpu: Remove struct fpu::counter

2018-10-13T07:18:58+00:00

commit 3913cc3507575273beb165a5e027a081913ed507 upstream.

With the lazy FPU code gone, we no longer use the counter field
in struct fpu for anything. Get rid it.

Signed-off-by: Rik van Riel 
Reviewed-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Thomas Gleixner 
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-6-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar 
Cc: Daniel Sangorrin 
Signed-off-by: Greg Kroah-Hartman

x86/fpu: Remove use_eager_fpu()

2018-10-13T07:18:58+00:00

commit c592b57347069abfc0dcad3b3a302cf882602597 upstream.

This removes all the obvious code paths that depend on lazy FPU mode.
It shouldn't change the generated code at all.

Signed-off-by: Andy Lutomirski 
Signed-off-by: Rik van Riel 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Thomas Gleixner 
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Daniel Sangorrin 
Signed-off-by: Greg Kroah-Hartman

x86: Don't include linux/irq.h from asm/hardirq.h

2018-08-15T16:14:52+00:00

commit 447ae316670230d7d29430e2cbf1f5db4f49d14c upstream

The next patch in this series will have to make the definition of
irq_cpustat_t available to entering_irq().

Inclusion of asm/hardirq.h into asm/apic.h would cause circular header
dependencies like

  asm/smp.h
    asm/apic.h
      asm/hardirq.h
        linux/irq.h
          linux/topology.h
            linux/smp.h
              asm/smp.h

or

  linux/gfp.h
    linux/mmzone.h
      asm/mmzone.h
        asm/mmzone_64.h
          asm/smp.h
            asm/apic.h
              asm/hardirq.h
                linux/irq.h
                  linux/irqdesc.h
                    linux/kobject.h
                      linux/sysfs.h
                        linux/kernfs.h
                          linux/idr.h
                            linux/gfp.h

and others.

This causes compilation errors because of the header guards becoming
effective in the second inclusion: symbols/macros that had been defined
before wouldn't be available to intermediate headers in the #include chain
anymore.

A possible workaround would be to move the definition of irq_cpustat_t
into its own header and include that from both, asm/hardirq.h and
asm/apic.h.

However, this wouldn't solve the real problem, namely asm/harirq.h
unnecessarily pulling in all the linux/irq.h cruft: nothing in
asm/hardirq.h itself requires it. Also, note that there are some other
archs, like e.g. arm64, which don't have that #include in their
asm/hardirq.h.

Remove the linux/irq.h #include from x86' asm/hardirq.h.

Fix resulting compilation errors by adding appropriate #includes to *.c
files as needed.

Note that some of these *.c files could be cleaned up a bit wrt. to their
set of #includes, but that should better be done from separate patches, if
at all.

Signed-off-by: Nicolai Stange 
Signed-off-by: Thomas Gleixner 
[dwmw2: More fixes for EFI and Xen in 4.9]
Signed-off-by: David Woodhouse 
Signed-off-by: Greg Kroah-Hartman

x86/fpu: Hard-disable lazy FPU mode

2018-06-16T07:52:32+00:00

commit ca6938a1cd8a1c5e861a99b67f84ac166fc2b9e7 upstream.

Since commit:

  58122bf1d856 ("x86/fpu: Default eagerfpu=on on all CPUs")

... in Linux 4.6, eager FPU mode has been the default on all x86
systems, and no one has reported any regressions.

This patch removes the ability to enable lazy mode: use_eager_fpu()
becomes "return true" and all of the FPU mode selection machinery is
removed.

Signed-off-by: Andy Lutomirski 
Signed-off-by: Rik van Riel 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Thomas Gleixner 
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

linux-stable.git/arch/x86/kernel/fpu, branch linux-4.9.y

x86/fpu: Make init_fpstate correct with optimized XSAVE

x86/fpu: Limit xstate copy size in xstateregs_set()

x86/fpu: Reset state for all signal restore failures

x86/pkeys: Add check for pkey "overflow"

x86/fpu: Disable bottom halves while loading FPU registers

x86/fpu: Remove second definition of fpu in __fpu__restore_sig()

x86/fpu: Remove struct fpu::counter

x86/fpu: Remove use_eager_fpu()

x86: Don't include linux/irq.h from asm/hardirq.h

x86/fpu: Hard-disable lazy FPU mode

x86/fpu: Remove second definition of fpu in fpurestore_sig()