| Date | Fri, 28 Dec 2012 20:04:07 +0100 | From | Ben Hutchings <> | Subject | [ 037/173] virtio: force vring descriptors to be allocated from lowmem |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon <will.deacon@arm.com>
commit b92b1b89a33c172c075edccf6afb0edc41d851fd upstream.
Virtio devices may attempt to add descriptors to a virtqueue from atomic context using GFP_ATOMIC allocation. This is problematic because such allocations can fall outside of the lowmem mapping, causing virt_to_phys to report bogus physical addresses which are subsequently passed to userspace via the buffers for the virtual device.
This patch masks out __GFP_HIGH and __GFP_HIGHMEM from the requested flags when allocating descriptors for a virtqueue. If an atomic allocation is requested and later fails, we will return -ENOSPC which will be handled by the driver.
Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- drivers/virtio/virtio_ring.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index e639584..286c30c 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -135,6 +135,13 @@ static int vring_add_indirect(struct vring_virtqueue *vq, unsigned head; int i; + /* + * We require lowmem mappings for the descriptors because + * otherwise virt_to_phys will give us bogus addresses in the + * virtqueue. + */ + gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH); + desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp); if (!desc) return -ENOMEM;
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