x86/CPU/AMD: Fix the DIV(0) initial fix attempt

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commit f58d6fbcb7 upstream.

Initially, it was thought that doing an innocuous division in the #DE
handler would take care to prevent any leaking of old data from the
divider but by the time the fault is raised, the speculation has already
advanced too far and such data could already have been used by younger
operations.

Therefore, do the innocuous division on every exit to userspace so that
userspace doesn't see any potentially old data from integer divisions in
kernel space.

Do the same before VMRUN too, to protect host data from leaking into the
guest too.

Fixes: 77245f1c3c ("x86/CPU/AMD: Do not leak quotient data after a division by 0")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20230811213824.10025-1-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Borislav Petkov (AMD) 2023-08-11 23:38:24 +02:00 • committed by Greg Kroah-Hartman

parent 48a558fbe8

commit 1251b96d79

4 changed files with 4 additions and 2 deletions

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arch/x86/include/asm/entry-common.h

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arch/x86/kernel/cpu/amd.c

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arch/x86/kernel/traps.c

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arch/x86/kvm/svm/svm.c

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