linux-kernel - [PATCH 3.16 156/212] s390/chsc: Add exception handler for CHSC instruction

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Message-ID: <lsq.1496331796.690355173@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:43:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Peter Oberparleiter" <oberpar@...ux.vnet.ibm.com>,
        "Cornelia Huck" <cornelia.huck@...ibm.com>,
        "Martin Schwidefsky" <schwidefsky@...ibm.com>,
        "Sebastian Ott" <sebott@...ux.vnet.ibm.com>
Subject: [PATCH 3.16 156/212] s390/chsc: Add exception handler for CHSC
 instruction

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>

commit 77759137248f34864a8f7a58bbcebfcf1047504a upstream.

Prevent kernel crashes due to unhandled exceptions raised by the CHSC
instruction which may for example be triggered by invalid ioctl data.

Fixes: 64150adf89df ("s390/cio: Introduce generic synchronous CHSC IOCTL")
Signed-off-by: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@...ux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/cio/ioasm.h | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/s390/cio/ioasm.h
+++ b/drivers/s390/cio/ioasm.h
@@ -138,13 +138,15 @@ static inline int tpi(struct tpi_info *a
 static inline int chsc(void *chsc_area)
 {
 	typedef struct { char _[4096]; } addr_type;
-	int cc;
+	int cc = -EIO;
 
 	asm volatile(
 		"	.insn	rre,0xb25f0000,%2,0\n"
-		"	ipm	%0\n"
+		"0:	ipm	%0\n"
 		"	srl	%0,28\n"
-		: "=d" (cc), "=m" (*(addr_type *) chsc_area)
+		"1:\n"
+		EX_TABLE(0b, 1b)
+		: "+d" (cc), "=m" (*(addr_type *) chsc_area)
 		: "d" (chsc_area), "m" (*(addr_type *) chsc_area)
 		: "cc");
 	return cc;