Commit b92b1b89 authored Oct 19, 2012 by Will Deacon Committed by Rusty Russell Oct 22, 2012

virtio: force vring descriptors to be allocated from lowmem



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: stable@kernel.org
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

parent b9cdc88d

drivers/virtio/virtio_ring.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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;