From: Will Deacon Date: Fri, 19 Oct 2012 13:03:33 +0000 (+0100) Subject: virtio: force vring descriptors to be allocated from lowmem X-Git-Tag: v3.4.25~62 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=6cb6a94380506d9e5491b8e145811bd676ce6f3d;p=platform%2Fkernel%2Flinux-stable.git virtio: force vring descriptors to be allocated from lowmem 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. Signed-off-by: Will Deacon Cc: Sasha Levin Signed-off-by: Rusty Russell Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 5aa43c3392a2..52bfd0786fc8 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -132,6 +132,13 @@ 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;