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Commit a14d749f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

virtio_blk: avoid DMA to stack for the sense buffer 



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: default avatarChristoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent dd545b52

drivers/block/virtio_blk.c

+3 −1
Original line number Original line Diff line number Diff line
@@ -56,6 +56,7 @@ struct virtblk_req { 
	struct virtio_blk_outhdr out_hdr;

	struct virtio_blk_outhdr out_hdr;

	struct virtio_scsi_inhdr in_hdr;

	struct virtio_scsi_inhdr in_hdr;

	u8 status;

	u8 status;

	u8 sense[SCSI_SENSE_BUFFERSIZE];

	struct scatterlist sg[];

	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)) {

	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;

		sgs[num_out + num_in++] = &sense;

		sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));

		sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));

		sgs[num_out + num_in++] = &inhdr;

		sgs[num_out + num_in++] = &inhdr;