| From b92b1b89a33c172c075edccf6afb0edc41d851fd Mon Sep 17 00:00:00 2001 |
| From: Will Deacon <will.deacon@arm.com> |
| Date: Fri, 19 Oct 2012 14:03:33 +0100 |
| Subject: virtio: force vring descriptors to be allocated from lowmem |
| |
| 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. |
| |
| Signed-off-by: Will Deacon <will.deacon@arm.com> |
| Cc: Sasha Levin <levinsasha928@gmail.com> |
| Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| drivers/virtio/virtio_ring.c | 7 +++++++ |
| 1 file changed, 7 insertions(+) |
| |
| --- a/drivers/virtio/virtio_ring.c |
| +++ b/drivers/virtio/virtio_ring.c |
| @@ -135,6 +135,13 @@ static int vring_add_indirect(struct vri |
| 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; |