linux-kernel - [PATCH v3 26/34] s390/ftrace: Unpoison ftrace_regs in kprobe_ftrace

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Message-ID: <20231213233605.661251-27-iii@linux.ibm.com>
Date:   Thu, 14 Dec 2023 00:24:46 +0100
From:   Ilya Leoshkevich <iii@...ux.ibm.com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Marco Elver <elver@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Pekka Enberg <penberg@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-s390@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>
Subject: [PATCH v3 26/34] s390/ftrace: Unpoison ftrace_regs in kprobe_ftrace_handler()

s390 uses assembly code to initialize ftrace_regs and call
kprobe_ftrace_handler(). Therefore, from the KMSAN's point of view,
ftrace_regs is poisoned on kprobe_ftrace_handler() entry. This causes
KMSAN warnings when running the ftrace testsuite.

Fix by trusting the assembly code and always unpoisoning ftrace_regs in
kprobe_ftrace_handler().

Reviewed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 arch/s390/kernel/ftrace.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index c46381ea04ec..3cc5e6d011a9 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -13,6 +13,7 @@
 #include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
+#include <linux/kmsan-checks.h>
 #include <linux/kprobes.h>
 #include <trace/syscall.h>
 #include <asm/asm-offsets.h>
@@ -300,6 +301,7 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 	if (bit < 0)
 		return;
 
+	kmsan_unpoison_memory(fregs, sizeof(*fregs));
 	regs = ftrace_get_regs(fregs);
 	p = get_kprobe((kprobe_opcode_t *)ip);
 	if (!regs || unlikely(!p) || kprobe_disabled(p))
-- 
2.43.0