x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code

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commit 83c133cf11 upstream.

The NMI entry code that switches to the normal kernel stack needs to
be very careful not to clobber any extra stack slots on the NMI
stack.  The code is fine under the assumption that SWAPGS is just a
normal instruction, but that assumption isn't really true.  Use
SWAPGS_UNSAFE_STACK instead.

This is part of a fix for some random crashes that Sasha saw.

Fixes: 9b6e6a8334 ("x86/nmi/64: Switch stacks on userspace NMI entry")
Reported-and-tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/974bc40edffdb5c2950a5c4977f821a446b76178.1442791737.git.luto@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ luis: backported to 3.16:
  - file rename: arch/x86/entry/entry_64.S -> arch/x86/kernel/entry_64.S
  - adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

...

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Andy Lutomirski 2015-09-20 16:32:05 -07:00 • committed by Luis Henriques

parent 938d2b3377

commit 528d9753b3

1 changed files with 4 additions and 1 deletions

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arch/x86/kernel/entry_64.S

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