From 81b6bde8ba0867910d5442c14c22cdb23d21cd84 Mon Sep 17 00:00:00 2001
From: Ilya Leoshkevich <iii@linux.ibm.com>
Date: Fri, 21 Jun 2024 13:35:11 +0200
Subject: [PATCH] s390/cpumf: unpoison STCCTM output buffer

stcctm() uses the "Q" constraint for dest, therefore KMSAN does not
understand that it fills multiple doublewords pointed to by dest, not just
one.  This results in false positives.

Unpoison the whole dest manually with kmsan_unpoison_memory().

Link: https://lkml.kernel.org/r/20240621113706.315500-28-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 arch/s390/include/asm/cpu_mf.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/s390/include/asm/cpu_mf.h b/arch/s390/include/asm/cpu_mf.h
index a0de5b9b02eaa..9e4bbc3e53f80 100644
--- a/arch/s390/include/asm/cpu_mf.h
+++ b/arch/s390/include/asm/cpu_mf.h
@@ -10,6 +10,7 @@
 #define _ASM_S390_CPU_MF_H
 
 #include <linux/errno.h>
+#include <linux/kmsan-checks.h>
 #include <asm/asm-extable.h>
 #include <asm/facility.h>
 
@@ -239,6 +240,11 @@ static __always_inline int stcctm(enum stcctm_ctr_set set, u64 range, u64 *dest)
 		: "=d" (cc)
 		: "Q" (*dest), "d" (range), "i" (set)
 		: "cc", "memory");
+	/*
+	 * If cc == 2, less than RANGE counters are stored, but it's not easy
+	 * to tell how many. Always unpoison the whole range for simplicity.
+	 */
+	kmsan_unpoison_memory(dest, range * sizeof(u64));
 	return cc;
 }
 
-- 
2.50.1