linux-kernel - [PATCH v6 35/44] x86: kmsan: handle open-coded assembly in lib/iomem.c

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Date:   Mon,  5 Sep 2022 14:24:43 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Christoph Hellwig <hch@....de>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kees Cook <keescook@...omium.org>,
        Marco Elver <elver@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Matthew Wilcox <willy@...radead.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v6 35/44] x86: kmsan: handle open-coded assembly in lib/iomem.c

KMSAN cannot intercept memory accesses within asm() statements.
That's why we add kmsan_unpoison_memory() and kmsan_check_memory() to
hint it how to handle memory copied from/to I/O memory.

Signed-off-by: Alexander Potapenko <glider@...gle.com>
---
Link: https://linux-review.googlesource.com/id/Icb16bf17269087e475debf07a7fe7d4bebc3df23
---
 arch/x86/lib/iomem.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
index 3e2f33fc33de2..e0411a3774d49 100644
--- a/arch/x86/lib/iomem.c
+++ b/arch/x86/lib/iomem.c
@@ -1,6 +1,7 @@
 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/io.h>
+#include <linux/kmsan-checks.h>
 
 #define movs(type,to,from) \
 	asm volatile("movs" type:"=&D" (to), "=&S" (from):"0" (to), "1" (from):"memory")
@@ -37,6 +38,8 @@ static void string_memcpy_fromio(void *to, const volatile void __iomem *from, si
 		n-=2;
 	}
 	rep_movs(to, (const void *)from, n);
+	/* KMSAN must treat values read from devices as initialized. */
+	kmsan_unpoison_memory(to, n);
 }
 
 static void string_memcpy_toio(volatile void __iomem *to, const void *from, size_t n)
@@ -44,6 +47,8 @@ static void string_memcpy_toio(volatile void __iomem *to, const void *from, size
 	if (unlikely(!n))
 		return;
 
+	/* Make sure uninitialized memory isn't copied to devices. */
+	kmsan_check_memory(from, n);
 	/* Align any unaligned destination IO */
 	if (unlikely(1 & (unsigned long)to)) {
 		movs("b", to, from);
-- 
2.37.2.789.g6183377224-goog