Re: [PATCH] Prevent out-of-bounds read/write in bcmasp_netfilt_rd and bcmasp_netfilt_wr

[Justin Chen]

On 11/3/23 5:57 AM, Greg KH wrote:
> On Fri, Nov 03, 2023 at 05:57:48PM +0530, Yuran Pereira wrote:
> > The functions `bcmasp_netfilt_rd` and `bcmasp_netfilt_wr` both call
> > `bcmasp_netfilt_get_reg_offset` which, when it fails, returns `-EINVAL`.
> > This could lead to an out-of-bounds read or write when `rx_filter_core_rl`
> > or `rx_filter_core_wl` is called.
> >
> > This patch adds a check in both functions to return immediately if
> > `bcmasp_netfilt_get_reg_offset` fails. This prevents potential out-of-bounds read
> > or writes, and ensures that no undefined or buggy behavior would originate from
> > the failure of `bcmasp_netfilt_get_reg_offset`.
> >
> > Addresses-Coverity-IDs: 1544536 ("Out-of-bounds access")
> > Signed-off-by: Yuran Pereira <yuran.pereira@xxxxxxxxxxx>
> > ---
> >   drivers/net/ethernet/broadcom/asp2/bcmasp.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/broadcom/asp2/bcmasp.c b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> > index 29b04a274d07..8b90b761bdec 100644
> > --- a/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> > +++ b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> > @@ -227,6 +227,8 @@ static void bcmasp_netfilt_wr(struct bcmasp_priv *priv,
> >   
> >   	reg_offset = bcmasp_netfilt_get_reg_offset(priv, nfilt, reg_type,
> >   						   offset);
> > +	if (reg_offset < 0)
> > +		return;
> >   
> >   	rx_filter_core_wl(priv, val, reg_offset);
> >   }
> > @@ -244,6 +246,8 @@ static u32 bcmasp_netfilt_rd(struct bcmasp_priv *priv,
> >   
> >   	reg_offset = bcmasp_netfilt_get_reg_offset(priv, nfilt, reg_type,
> >   						   offset);
> > +	if (reg_offset < 0)
> > +		return 0;
>
> Shouldn't you return an error here?
>
> thanks
>
> greg k-h

As long as offset is less than MAX_WAKE_FILTER_SIZE we don't need to 
worry about error checking. This is already checked before we call 
netfilt_get_reg_offset() in both cases. Instead of returning -EINVAL in 
neffilt_get_reg_offset() lets return 0. This will silence the coverity 
check. In practice we will never hit this logic.

Thanks,
Justin

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