From: Greg KH <gre...@linuxfoundation.org>
3.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Wang Sen <senw...@linux.vnet.ibm.com>
commit 27e99ade81368e6fdda3212bff9345177cf9e57a upstream.
When using the commands below to write some data to a virtio-scsi LUN of the
QEMU guest(32-bit) with 1G physical memory(qemu -m 1024), the qemu will crash.
# sudo mkfs.ext4 /dev/sdb (/dev/sdb is the virtio-scsi LUN.)
# sudo mount /dev/sdb /mnt
# dd if=/dev/zero of=/mnt/file bs=1M count=1024
In current implementation, sg_set_buf is called to add buffers to sg list which
is put into the virtqueue eventually. But if there are some HighMem pages in
table->sgl you can not get virtual address by sg_virt. So, sg_virt(sg_elem) may
return NULL value. This will cause QEMU exit when virtqueue_map_sg is called
in QEMU because an invalid GPA is passed by virtqueue.
Two solutions are discussed here:
http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/00675.html
Finally, value assignment approach was adopted because:
Value assignment creates a well-formed scatterlist, because the termination
marker in source sg_list has been set in blk_rq_map_sg(). The last entry of the
source sg_list is just copied to the the last entry in destination list. Note
that, for now, virtio_ring does not care about the form of the scatterlist and
simply processes the first out_num + in_num consecutive elements of the sg[]
array.
I have tested the patch on my workstation. QEMU would not crash any more.
Signed-off-by: Wang Sen <senw...@linux.vnet.ibm.com>
Acked-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: James Bottomley <jbottom...@parallels.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/scsi/virtio_scsi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -198,7 +198,7 @@ static void virtscsi_map_sgl(struct scat
int i;
for_each_sg(table->sgl, sg_elem, table->nents, i)
- sg_set_buf(&sg[idx++], sg_virt(sg_elem), sg_elem->length);
+ sg[idx++] = *sg_elem;
*p_idx = idx;
}
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