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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: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org # v4.9+
Signed-off-by: Jens Axboe <axboe@fb.com>
hifive-unleashed-5.1
Christoph Hellwig 2017-01-09 08:56:23 -07:00 committed by Jens Axboe
parent dd545b52a3
commit a14d749fce
1 changed files with 3 additions and 1 deletions
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4
drivers/block/virtio_blk.c
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@ -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);
sgs[num_out + num_in++] = &sense;
sg_init_one(&inhdr, &vbr->in_hdr, sizeof(vbr->in_hdr));
sgs[num_out + num_in++] = &inhdr;