linux-kernel - Re: [PATCH] mailbox: imx-mailbox: fix scu msg header size check

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Date:   Tue, 14 Apr 2020 12:31:51 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Peng Fan <peng.fan@....com>
Cc:     "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
        "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>,
        Leonard Crestez <leonard.crestez@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        Anson Huang <anson.huang@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mailbox: imx-mailbox: fix scu msg header size check

On Tue, Apr 14, 2020 at 08:40:19AM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH] mailbox: imx-mailbox: fix scu msg header size check
> > 
> > On Tue, Apr 14, 2020 at 04:10:26PM +0800, peng.fan@....com wrote:
> > > From: Peng Fan <peng.fan@....com>
> > >
> > > The i.MX8 SCU message header size is the number of "u32" elements, not
> > > "u8", so fix the check.
> > >
> > > Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
> > > Addresses-Coverity-ID: 1461658 ("Memory - corruptions")
> > > Signed-off-by: Peng Fan <peng.fan@....com>
> > > ---
> > >
> > > V2:
> > >  I not include the fixes tag, since this patch still in next tree.
> > >
> > >  drivers/mailbox/imx-mailbox.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/mailbox/imx-mailbox.c
> > > b/drivers/mailbox/imx-mailbox.c index 7906624a731c..c2398cb63ea0
> > > 100644
> > > --- a/drivers/mailbox/imx-mailbox.c
> > > +++ b/drivers/mailbox/imx-mailbox.c
> > > @@ -154,12 +154,12 @@ static int imx_mu_scu_tx(struct imx_mu_priv
> > > *priv,
> > >
> > >  	switch (cp->type) {
> > >  	case IMX_MU_TYPE_TX:
> > > -		if (msg->hdr.size > sizeof(*msg)) {
> > > +		if (msg->hdr.size > (sizeof(*msg) / 4)) {
> > 
> > No need for the parenthesis. Maybe a comment would be helpful here,
> > something like:
> > 
> > 	/*
> > 	 * msg->hdr.size specifies the number of u32 words while sizeof
> > 	 * yields bytes.
> > 	 */
> 
> V2 will have the update.
> 
> > 
> > >  			/*
> > >  			 * The real message size can be different to
> > >  			 * struct imx_sc_rpc_msg_max size
> > >  			 */
> > > -			dev_err(priv->dev, "Exceed max msg size (%zu) on TX,
> > got: %i\n", sizeof(*msg), msg->hdr.size);
> > > +			dev_err(priv->dev, "Exceed max msg size (%zu) on TX,
> > got: %i\n",
> > > +sizeof(*msg) / 4, msg->hdr.size);
> > 
> > The unit here is also "number of u32 words", maybe bytes is more natural?
> 
> ok. Will change to msg->hdr.size << 2 keeping sizeof(*msg).
> 
> > And I suggesting specifying the unit in the error message.
> 
> Is this ok to you?
> dev_err(priv->dev, "Exceed max msg size (%zu) on TX, got: %i, 
> msg->hdr.size: %i\n", sizeof(*msg), msg->hdr.size << 2, msg->hdr.size);

I'd prefer:

	dev_err(priv->dev, "Maximal message size (%zu bytes) exceeded on TX; got: %i bytes\n"

. Duplicating the value doesn't add much value.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |