From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: [PATCH v2 3/3] virtio: force vring descriptors to be allocated from lowmem Date: Fri, 19 Oct 2012 14:03:33 +0100 Message-ID: <1350651813-8694-3-git-send-email-will.deacon@arm.com> References: <1350651813-8694-1-git-send-email-will.deacon@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1350651813-8694-1-git-send-email-will.deacon@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: linux-kernel@vger.kernel.org Cc: Marc.Zyngier@arm.com, Will Deacon , virtualization@lists.linux-foundation.org, ericvh@gmail.com, levinsasha928@gmail.com, akpm@linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org 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: Rusty Russell Cc: Sasha Levin Signed-off-by: Will Deacon --- drivers/virtio/virtio_ring.c | 7 +++++++ 1 files changed, 7 insertions(+), 0 deletions(-) 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; -- 1.7.4.1