Re: [PATCH v3 8/9] cxl/mbox: Block immediate mode in SET_PARTITION_INFO command

[Alison Schofield <alison.schofield@intel.com>]

On Fri, Mar 25, 2022 at 11:18:16AM +0000, Jonathan Cameron wrote:
> On Wed, 23 Mar 2022 18:11:25 -0700
> alison.schofield@intel.com wrote:
> 
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > User space may send the SET_PARTITION_INFO mailbox command using
> > the IOCTL interface. Inspect the input payload and fail if the
> > immediate flag is set.
> > 
> > This is the first instance of the driver inspecting an input payload
> > from user space. Assume there will be more such cases and implement
> > with an extensible helper.
> > 
> > In order for the kernel to react to an immediate partition change it
> > needs to assert that the change will not affect any active decode. At
> > a minimum this requires validating that the device is using HDM
> > decoders instead of the CXL DVSEC for decode, and that none of the
> > active HDM decoders are affected by the partition change. For now,
> > just fail until that support arrives.
> > 
> > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> 
> Follow on comment from one in earlier patch on the use of a goto
> to skip the input payload case... Otherwise,
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>
snip
> >  static int cxl_to_mbox_cmd(struct cxl_dev_state *cxlds,
> >  			   struct cxl_mbox_cmd *mbox, u16 opcode,
> >  			   size_t in_size, size_t out_size, u64 in_payload)
> > @@ -235,6 +269,13 @@ static int cxl_to_mbox_cmd(struct cxl_dev_state *cxlds,
> >  	if (!mbox->payload_in)
> >  		return PTR_ERR(mbox->payload_in);
> >  
> > +	if (!cxl_payload_from_user_allowed(opcode, mbox->payload_in)) {
> > +		dev_dbg(cxlds->dev, "%s: input payload not allowed\n",
> > +			cxl_mem_opcode_to_name(opcode));
> > +		kvfree(mbox->payload_in);
> > +		return -EBUSY;
> > +	}
> 
> Ah. This is making the block before the label larger. I'm still doubtful that
> the code is more readable with the goto though rather than just having
> it indented one more tab.
> 
You remembered my goto from a few patches back and still don't
appreciate it ;)
Will redo.
Thanks for the reviews Jonathan!