[PATCH v2 2/3] virtio: 9p: correctly pass physical address to userspace for high pages

From: Will Deacon
Date: Fri Oct 19 2012 - 09:03:56 EST

When using a virtio transport, the 9p net device may pass the physical
address of a kernel buffer to userspace via a scatterlist inside a
virtqueue. If the kernel buffer is mapped outside of the linear mapping
(e.g. highmem), then virt_to_page will return a bogus value and we will
populate the scatterlist with junk.

This patch uses kmap_to_page when populating the page array for a kernel

Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Sasha Levin <levinsasha928@xxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
net/9p/trans_virtio.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 35b8911..fd05c81 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -39,6 +39,7 @@
#include <linux/inet.h>
#include <linux/idr.h>
#include <linux/file.h>
+#include <linux/highmem.h>
#include <linux/slab.h>
#include <net/9p/9p.h>
#include <linux/parser.h>
@@ -325,7 +326,7 @@ static int p9_get_mapped_pages(struct virtio_chan *chan,
int count = nr_pages;
while (nr_pages) {
s = rest_of_page(data);
- pages[index++] = virt_to_page(data);
+ pages[index++] = kmap_to_page(data);
data += s;

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