3.5.7.3 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.dea...@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.
Cc: Sasha Levin <levinsasha...@gmail.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesin...@canonical.com>
---
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 5aa43c3..52bfd07 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -132,6 +132,13 @@ 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;
--
1.7.9.5
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