From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754841Ab2L1T0l (ORCPT ); Fri, 28 Dec 2012 14:26:41 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55652 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932430Ab2L1TTm (ORCPT ); Fri, 28 Dec 2012 14:19:42 -0500 Message-Id: <20121228190337.671243871@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Fri, 28 Dec 2012 20:04:07 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Will Deacon , Sasha Levin , Rusty Russell Subject: [ 037/173] virtio: force vring descriptors to be allocated from lowmem In-Reply-To: <20121228190330.025298996@decadent.org.uk> X-SA-Exim-Connect-IP: 151.217.219.220 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon 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 Signed-off-by: Will Deacon Signed-off-by: Rusty Russell Signed-off-by: Ben Hutchings --- 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;