linux-kernel - [PATCH 3/3] vhost: make default mapping empty by default

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Date:	Sun, 20 Dec 2009 19:16:32 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Cc:	Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 3/3] vhost: make default mapping empty by default

vhost now validates each region with access_ok in calling process
context before access.  Since this fails on a full 64 bit 1:1 mapping
that vhost had by default, we can't support such a mapping: users will
have to set up a table with real addresses that actually matches their
address space.
Make the default mapping empty.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/vhost/vhost.c |   13 +++----------
 1 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 33e06bf..2b65d9b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -170,21 +170,14 @@ long vhost_dev_reset_owner(struct vhost_dev *dev)
 {
 	struct vhost_memory *memory;
 
-	/* Restore memory to default 1:1 mapping. */
-	memory = kmalloc(offsetof(struct vhost_memory, regions) +
-			 2 * sizeof *memory->regions, GFP_KERNEL);
+	/* Restore memory to default empty mapping. */
+	memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
 	if (!memory)
 		return -ENOMEM;
 
 	vhost_dev_cleanup(dev);
 
-	memory->nregions = 2;
-	memory->regions[0].guest_phys_addr = 1;
-	memory->regions[0].userspace_addr = 1;
-	memory->regions[0].memory_size = ~0ULL;
-	memory->regions[1].guest_phys_addr = 0;
-	memory->regions[1].userspace_addr = 0;
-	memory->regions[1].memory_size = 1;
+	memory->nregions = 0;
 	dev->memory = memory;
 	return 0;
 }
-- 
1.6.6.rc1.43.gf55cc
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