linux-kernel - [PATCH v3 25/46] kmsan: virtio: check/unpoison scatterlist in vring_map_one

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Message-Id: <20220426164315.625149-26-glider@google.com>
Date:   Tue, 26 Apr 2022 18:42:54 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     glider@...gle.com
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        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 v3 25/46] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg()

If vring doesn't use the DMA API, KMSAN is unable to tell whether the
memory is initialized by hardware. Explicitly call kmsan_handle_dma()
from vring_map_one_sg() in this case to prevent false positives.

Signed-off-by: Alexander Potapenko <glider@...gle.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>

---
Link: https://linux-review.googlesource.com/id/I211533ecb86a66624e151551f83ddd749536b3af
---
 drivers/virtio/virtio_ring.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cfb028ca238eb..faecd9e3d6560 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/hrtimer.h>
 #include <linux/dma-mapping.h>
+#include <linux/kmsan-checks.h>
 #include <linux/spinlock.h>
 #include <xen/xen.h>
 
@@ -331,8 +332,15 @@ static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
 				   struct scatterlist *sg,
 				   enum dma_data_direction direction)
 {
-	if (!vq->use_dma_api)
+	if (!vq->use_dma_api) {
+		/*
+		 * If DMA is not used, KMSAN doesn't know that the scatterlist
+		 * is initialized by the hardware. Explicitly check/unpoison it
+		 * depending on the direction.
+		 */
+		kmsan_handle_dma(sg_page(sg), sg->offset, sg->length, direction);
 		return (dma_addr_t)sg_phys(sg);
+	}
 
 	/*
 	 * We can't use dma_map_sg, because we don't use scatterlists in
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog