linux-kernel - [PATCH 17/32] lib/string: Add KMSAN support to strlcpy() and strlcat()

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Message-ID: <20231115203401.2495875-18-iii@linux.ibm.com>
Date:   Wed, 15 Nov 2023 21:30:49 +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>,
        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 17/32] lib/string: Add KMSAN support to strlcpy() and strlcat()

Currently KMSAN does not fully propagate metadata in strlcpy() and
strlcat(), because they are built with -ffreestanding and call
memcpy(). In this combination memcpy() calls are not instrumented.

Fix by copying the metadata manually. Add the __STDC_HOSTED__ #ifdef in
case the code is compiled with different flags in the future.

Signed-off-by: Ilya Leoshkevich <iii@...ux.ibm.com>
---
 lib/string.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/string.c b/lib/string.c
index be26623953d2..e83c6dd77ec6 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -111,6 +111,9 @@ size_t strlcpy(char *dest, const char *src, size_t size)
 	if (size) {
 		size_t len = (ret >= size) ? size - 1 : ret;
 		__builtin_memcpy(dest, src, len);
+#if __STDC_HOSTED__ == 0
+		kmsan_memmove_metadata(dest, src, len);
+#endif
 		dest[len] = '\0';
 	}
 	return ret;
@@ -261,6 +264,9 @@ size_t strlcat(char *dest, const char *src, size_t count)
 	if (len >= count)
 		len = count-1;
 	__builtin_memcpy(dest, src, len);
+#if __STDC_HOSTED__ == 0
+	kmsan_memmove_metadata(dest, src, len);
+#endif
 	dest[len] = 0;
 	return res;
 }
-- 
2.41.0