This is a note to let you know that I've just added the patch titled
s390/ctl_reg: make __ctl_load a full memory barrier
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-ctl_reg-make-__ctl_load-a-full-memory-barrier.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Mon Jul 3 13:41:44 CEST 2017
From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Date: Wed, 28 Dec 2016 11:33:48 +0100
Subject: s390/ctl_reg: make __ctl_load a full memory barrier
From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
[ Upstream commit e991c24d68b8c0ba297eeb7af80b1e398e98c33f ]
We have quite a lot of code that depends on the order of the
__ctl_load inline assemby and subsequent memory accesses, like
e.g. disabling lowcore protection and the writing to lowcore.
Since the __ctl_load macro does not have memory barrier semantics, nor
any other dependencies the compiler is, theoretically, free to shuffle
code around. Or in other words: storing to lowcore could happen before
lowcore protection is disabled.
In order to avoid this class of potential bugs simply add a full
memory barrier to the __ctl_load macro.
Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/ctl_reg.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/s390/include/asm/ctl_reg.h
+++ b/arch/s390/include/asm/ctl_reg.h
@@ -15,7 +15,9 @@
BUILD_BUG_ON(sizeof(addrtype) != (high - low + 1) * sizeof(long));\
asm volatile( \
" lctlg %1,%2,%0\n" \
- : : "Q" (*(addrtype *)(&array)), "i" (low), "i" (high));\
+ : \
+ : "Q" (*(addrtype *)(&array)), "i" (low), "i" (high) \
+ : "memory"); \
}
#define __ctl_store(array, low, high) { \
Patches currently in stable-queue which might be from heiko.carstens@xxxxxxxxxx are
queue-4.4/s390-ctl_reg-make-__ctl_load-a-full-memory-barrier.patch