Patch "s390: fix test_fp_ctl inline assembly contraints" has been added to the 4.6-stable tree

Patch "s390: fix test_fp_ctl inline assembly contraints" has been added to the 4.6-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    s390: fix test_fp_ctl inline assembly contraints

to the 4.6-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-fix-test_fp_ctl-inline-assembly-contraints.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From bcf4dd5f9ee096bd1510f838dd4750c35df4e38b Mon Sep 17 00:00:00 2001
From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Mon, 27 Jun 2016 17:06:45 +0200
Subject: s390: fix test_fp_ctl inline assembly contraints

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

commit bcf4dd5f9ee096bd1510f838dd4750c35df4e38b upstream.

The test_fp_ctl function is used to test if a given value is a valid
floating-point control. The inline assembly in test_fp_ctl uses an
incorrect constraint for the 'orig_fpc' variable. If the compiler
chooses the same register for 'fpc' and 'orig_fpc' the test_fp_ctl()
function always returns true. This allows user space to trigger
kernel oopses with invalid floating-point control values on the
signal stack.

This problem has been introduced with git commit 4725c86055f5bbdcdf
"s390: fix save and restore of the floating-point-control register"

Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/include/asm/fpu/api.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/include/asm/fpu/api.h
+++ b/arch/s390/include/asm/fpu/api.h
@@ -22,7 +22,7 @@ static inline int test_fp_ctl(u32 fpc)
 		"	la	%0,0\n"
 		"1:\n"
 		EX_TABLE(0b,1b)
-		: "=d" (rc), "=d" (orig_fpc)
+		: "=d" (rc), "=&d" (orig_fpc)
 		: "d" (fpc), "0" (-EINVAL));
 	return rc;
 }


Patches currently in stable-queue which might be from schwidefsky@de.ibm.com are

queue-4.6/s390-fix-test_fp_ctl-inline-assembly-contraints.patch
queue-4.6/kvm-s390-mm-fix-cmma-reset-during-reboot.patch
queue-4.6/revert-s390-kdump-clear-subchannel-id-to-signal-non-ccw-scsi-ipl.patch