Patch "virtio_blk: avoid DMA to stack for the sense buffer" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

virtio_blk: avoid DMA to stack for the sense buffer

to the 4.9-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_blk-avoid-dma-to-stack-for-the-sense-buffer.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Christoph Hellwig <[email protected]>
Date: Mon, 9 Jan 2017 08:56:23 -0700
Subject: virtio_blk: avoid DMA to stack for the sense buffer

From: Christoph Hellwig <[email protected]>

commit a14d749fcebe97ddf6af6db3d1f6ece85c9ddcb9 upstream.

Most users of BLOCK_PC requests allocate the sense buffer on the stack, so to avoid DMA to the stack copy them to a field in the heap allocated virtblk_req structure. Without that any attempt at SCSI passthrough I/O, including the SG_IO ioctl from userspace will crash the kernel. Note that this includes running tools like hdparm even when the host does not have SCSI passthrough enabled.

---
 drivers/block/virtio_blk.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -56,6 +56,7 @@ struct virtblk_req {
 	struct virtio_blk_outhdr out_hdr;
 	struct virtio_scsi_inhdr in_hdr;
 	u8 status;
+	u8 sense[SCSI_SENSE_BUFFERSIZE];
 	struct scatterlist sg[];
 };
 

@@ -102,7 +103,8 @@ static int __virtblk_add_req(struct virt
 	}
 
 	if (type == cpu_to_virtio32(vq->vdev, VIRTIO_BLK_T_SCSI_CMD)) {
-		sg_init_one(&sense, vbr->req->sense, SCSI_SENSE_BUFFERSIZE);
+		memcpy(vbr->sense, vbr->req->sense, SCSI_SENSE_BUFFERSIZE);
+		sg_init_one(&sense, vbr->sense, SCSI_SENSE_BUFFERSIZE);
 		sgs[num_out + num_in++] = &sense;
 		sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));
 		sgs[num_out + num_in++] = &inhdr;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/nvme-apply-delay_before_chk_rdy-quirk-at-probe-time-too.patch queue-4.9/mm-fix-devm_memremap_pages-crash-use-mem_hotplug_-begin-done.patch queue-4.9/virtio_blk-avoid-dma-to-stack-for-the-sense-buffer.patch