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Commit 83c133cf authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
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x86/nmi/64: Fix a paravirt stack-clobbering bug in the NMI code



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: 9b6e6a83 ("x86/nmi/64: Switch stacks on userspace NMI entry")
Reported-and-tested-by: default avatarSasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/974bc40edffdb5c2950a5c4977f821a446b76178.1442791737.git.luto@kernel.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent fc57a7c6
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