Subject: Re: [PATCH net 1/1] net: dsa: mv88e6xxx: Fix out-of-bound access

From: Simon Horman <[email-masked]>
Date: Tue, 20 Aug 2024 19:32:02 +0100

On Tue, Aug 20, 2024 at 12:58:05AM +0200, Andrew Lunn wrote:
> On Mon, Aug 19, 2024 at 06:26:40PM -0400, Joseph Huang wrote:
> > If an ATU violation was caused by a CPU Load operation, the SPID is 0xf,
> > which is larger than DSA_MAX_PORTS (the size of mv88e6xxx_chip.ports[]
> > array).
> 
> The 6390X datasheet says "IF SPID = 0x1f the source of the violation
> was the CPU's registers interface."
> 
> > +#define MV88E6XXX_G1_ATU_DATA_SPID_CPU				0x000f
> 
> So it seems to depend on the family.
> 
> >  
> >  /* Offset 0x0D: ATU MAC Address Register Bytes 0 & 1
> >   * Offset 0x0E: ATU MAC Address Register Bytes 2 & 3
> > diff --git a/drivers/net/dsa/mv88e6xxx/global1_atu.c b/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > index ce3b3690c3c0..b6f15ae22c20 100644
> > --- a/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > +++ b/drivers/net/dsa/mv88e6xxx/global1_atu.c
> > @@ -457,7 +457,8 @@ static irqreturn_t mv88e6xxx_g1_atu_prob_irq_thread_fn(int irq, void *dev_id)
> >  		trace_mv88e6xxx_atu_full_violation(chip->dev, spid,
> >  						   entry.portvec, entry.mac,
> >  						   fid);
> > -		chip->ports[spid].atu_full_violation++;
> > +		if (spid != MV88E6XXX_G1_ATU_DATA_SPID_CPU)
> > +			chip->ports[spid].atu_full_violation++;
> 
> So i think it would be better to do something like:
> 
> 		if (spid < ARRAY_SIZE(chip->ports))
> 			chip->ports[spid].atu_full_violation++;

Hi Joseph,

I am curious to know if bounds checking should also
be added to other accesses to chip->ports[spid] within this function.