From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: axboe@kernel.dk, jasowang@redhat.com,
linux-block@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] virtio_blk: avoid DMA to stack for the sense buffer
Date: Mon, 9 Jan 2017 18:33:09 +0200 [thread overview]
Message-ID: <20170109183053-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <1483507505-26797-2-git-send-email-hch@lst.de>
On Wed, Jan 04, 2017 at 08:25:05AM +0300, Christoph Hellwig wrote:
> 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.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/block/virtio_blk.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 5545a67..3c3b8f6 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -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 virtqueue *vq,
> }
>
> 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);
I would prefer sizeof(vbr->sense) here to avoid duplication.
Otherwise:
Acked-by: Michael S. Tsirkin <mst@redhat.com>
> sgs[num_out + num_in++] = &sense;
> sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));
> sgs[num_out + num_in++] = &inhdr;
> --
> 2.1.4
prev parent reply other threads:[~2017-01-09 16:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-04 5:25 4.10 and -stable fix for virtio_blk and virtually mapped stacks Christoph Hellwig
2017-01-04 5:25 ` [PATCH] virtio_blk: avoid DMA to stack for the sense buffer Christoph Hellwig
2017-01-04 7:44 ` Jason Wang
2017-01-09 13:35 ` Christoph Hellwig
2017-01-09 15:56 ` Jens Axboe
2017-01-04 15:47 ` 王金浦
2017-01-05 9:57 ` Christoph Hellwig
2017-01-05 10:37 ` 王金浦
2017-01-05 11:17 ` Christoph Hellwig
2017-01-09 16:33 ` Michael S. Tsirkin [this message]
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