linux-kernel - Re: [PATCH 1/1] i3c: master: svc: return error when read length bigger than 255

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Date: Thu, 11 Jan 2024 12:29:00 -0500
From: Frank Li <Frank.li@....com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: conor.culhane@...vaco.com, imx@...ts.linux.dev, joe@...ches.com,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
	miquel.raynal@...tlin.com, zbigniew.lukwinski@...ux.intel.com
Subject: Re: [PATCH 1/1] i3c: master: svc: return error when read length
 bigger than 255

On Thu, Jan 11, 2024 at 01:15:23AM +0100, Alexandre Belloni wrote:
> On 10/01/2024 17:25:03-0500, Frank Li wrote:
> > RDTERM in MCTRL is 8 bits. Add a length check to prevent silent data errors
> > when the read length exceeds 255 bytes during each i3c_priv_xfer operation.
> > 
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> >  drivers/i3c/master/svc-i3c-master.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> > index bd10bb698da0f..181b56953fb28 100644
> > --- a/drivers/i3c/master/svc-i3c-master.c
> > +++ b/drivers/i3c/master/svc-i3c-master.c
> > @@ -1375,6 +1375,11 @@ static int svc_i3c_master_priv_xfers(struct i3c_dev_desc *dev,
> >  		cmd->len = xfers[i].len;
> >  		cmd->actual_len = xfers[i].rnw ? xfers[i].len : 0;
> >  		cmd->continued = (i + 1) < nxfers;
> > +
> > +		if (cmd->rnw && cmd->len > 255) {
> > +			dev_err(master->dev, "only support read less than 255 each xfer\n");
> 
> What would be the end user action upon seeing this message? Is it actually
> useful?

Hold on, I found an method. It may support > 255 transfer.

Frank Li

> 
> > +			return -EINVAL;
> > +		}
> >  	}
> >  
> >  	mutex_lock(&master->lock);
> > -- 
> > 2.34.1
> > 
> 
> -- 
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com