On Fri, Dec 23, 2016 at 2:00 AM, Christoph Hellwig <h...@lst.de> wrote: > > From: Christoph Hellwig <h...@lst.de> > Date: Fri, 23 Dec 2016 10:57:06 +0100 > Subject: 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.
Ugh. This patch is nasty. I think we should just fix blk_execute_rq() instead. But from a quick look, we also have at least sg_scsi_ioctl() and sg_io() doing the same thing. And the SG_IO thing in bsg_ioctl(). And spi_execute() in scsi_transport_spi.c And resp_requests() in scsi_debug.c. So I guess ugly it may need to be, and the rule is that the sense buffer really can be on the stack and you can't DMA to/from it. Comments from others? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html