This is a note to let you know that I've just added the patch titled
virtio: force vring descriptors to be allocated from lowmem
to the 3.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio-force-vring-descriptors-to-be-allocated-from-lowmem.patch
and it can be found in the queue-3.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From b92b1b89a33c172c075edccf6afb0edc41d851fd Mon Sep 17 00:00:00 2001
From: Will Deacon <[email protected]>
Date: Fri, 19 Oct 2012 14:03:33 +0100
Subject: virtio: force vring descriptors to be allocated from lowmem
From: Will Deacon <[email protected]>
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 <[email protected]>
Cc: Sasha Levin <[email protected]>
Signed-off-by: Rusty Russell <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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;
Patches currently in stable-queue which might be from [email protected] are
queue-3.7/mm-highmem-export-kmap_to_page-for-modules.patch
queue-3.7/arm64-signal-push-the-unwinding-prologue-on-the-signal-stack.patch
queue-3.7/virtio-9p-correctly-pass-physical-address-to-userspace-for-high-pages.patch
queue-3.7/virtio-force-vring-descriptors-to-be-allocated-from-lowmem.patch
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