linux-kernel - Re: [PATCH 4/7] soc: aspeed: lpc-snoop: Constrain parameters in channel paths

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Message-ID: <6a4e31eeed722f9c36302d3d097cb054465c82c2.camel@codeconstruct.com.au>
Date: Thu, 17 Apr 2025 09:07:59 +0930
From: Andrew Jeffery <andrew@...econstruct.com.au>
To: Jean Delvare <jdelvare@...e.de>
Cc: Joel Stanley <joel@....id.au>, Henry Martin <bsdhenrymartin@...il.com>, 
 Patrick Rudolph <patrick.rudolph@...ements.com>, Andrew Geissler
 <geissonator@...oo.com>, Ninad Palsule <ninad@...ux.ibm.com>, Patrick
 Venture <venture@...gle.com>, Robert Lippert <roblip@...il.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/7] soc: aspeed: lpc-snoop: Constrain parameters in
 channel paths

On Wed, 2025-04-16 at 14:37 +0200, Jean Delvare wrote:
> On Fri, 11 Apr 2025 10:38:34 +0930, Andrew Jeffery wrote:
> > Ensure pointers and the channel index are valid before use.
> > 
> > Fixes: 9f4f9ae81d0a ("drivers/misc: add Aspeed LPC snoop driver")
> 
> Please don't abuse Fixes tags. Here you are hardening the code just in
> case, but this isn't fixing any actual bug, as functions
> aspeed_lpc_enable_snoop() and aspeed_lpc_disable_snoop() were never
> called with an incorrect channel index.

I'll drop the tag.

> 
> > Signed-off-by: Andrew Jeffery <andrew@...econstruct.com.au>
> > ---
> >  drivers/soc/aspeed/aspeed-lpc-snoop.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> > index 28f034b8a3b7226efe20cbe30a7da0c2b49fbd96..6ab362aeb180c8ad356422d8257717f41a232b3c 100644
> > --- a/drivers/soc/aspeed/aspeed-lpc-snoop.c
> > +++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c
> > @@ -182,6 +182,7 @@ static int aspeed_lpc_snoop_config_irq(struct aspeed_lpc_snoop *lpc_snoop,
> >         return 0;
> >  }
> >  
> > +__attribute__((nonnull))
> >  static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> >                                    struct device *dev,
> >                                    int channel, u16 lpc_port)
> > @@ -190,6 +191,8 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> >         u32 hicr5_en, snpwadr_mask, snpwadr_shift, hicrb_en;
> >         int rc = 0;
> >  
> > +       if (channel < 0 || channel >= ARRAY_SIZE(lpc_snoop->chan))
> > +               return -EINVAL;
> >  
> >         if (lpc_snoop->chan[channel].enabled)
> >                 return -EBUSY;
> > @@ -252,9 +255,13 @@ static int aspeed_lpc_enable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> >         return rc;
> >  }
> >  
> > +__attribute__((nonnull))
> >  static void aspeed_lpc_disable_snoop(struct aspeed_lpc_snoop *lpc_snoop,
> >                                      int channel)
> >  {
> > +       if (channel < 0 || channel >= ARRAY_SIZE(lpc_snoop->chan))
> > +               return;
> > +
> >         if (!lpc_snoop->chan[channel].enabled)
> >                 return;
> >  
> > 
> 
> TBH I'm not sure if this has much value, as any error in the channel
> index (or passing NULL pointers for lpc_snoop or dev) would likely be
> caught very early during driver development or update. And silently
> returning early is not going to fix the problem if this ever happens.
> 
> But well, I'm not much into defensive programming anyway, so maybe this
> is just me. As I'm not maintaining this driver, this ain't my decision.
> 
> Acked-by: Jean Delvare <jdelvare@...e.de>
> 

Given there's some other minor cleanups in your review of the series
I'll reconsider this approach as well.

Andrew