linux-kernel - [PATCH 3.4 49/88] virtio: 9p: correctly pass physical address to userspace for high pages

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Date:	Mon,  9 Jun 2014 17:24:59 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Sasha Levin <levinsasha928@...il.com>,
	Will Deacon <will.deacon@....com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ben Hutchings <ben@...adent.org.uk>,
	Yijing Wang <wangyijing@...wei.com>
Subject: [PATCH 3.4 49/88] virtio: 9p: correctly pass physical address to userspace for high pages

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.deacon@....com>

commit 30d395b124c51db66d9f3ba0611cd62021afc392 upstream.

commit b9cdc88df8e63e81c723b82c286fc97f5d0dc325 upstream.

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
buffer.

Cc: Sasha Levin <levinsasha928@...il.com>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: Yijing Wang <wangyijing@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/9p/trans_virtio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- 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 vi
 		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;
 			nr_pages--;
 		}


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