Subject: Re: [PATCH net 1/2] net/ethernet/chelsio: fix cxgb4_getpgtccfg wrong memory access

From: Leon Romanovsky <[email-masked]>
Date: Tue, 17 Jan 2023 11:21:34 +0200

On Mon, Jan 16, 2023 at 06:20:59PM +0300, Maksim Davydov wrote:
> *pgid can be in range 0 to 0xF (bitmask 0xF) but valid values for PGID
> are between 0 and 7. Also the size of pgrate is 8. Thus, we are needed
> additional check to make sure that this code doesn't have access to tsa.
> 
> Found by Linux Verification Center (linuxtesting.org) with the SVACE
> static analysis tool.
> 
> Fixes: 76bcb31efc06 ("cxgb4 : Add DCBx support codebase and dcbnl_ops")
> Signed-off-by: Maksim Davydov <[email-masked]>
> ---
>  drivers/net/ethernet/chelsio/cxgb4/cxgb4_dcb.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_dcb.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_dcb.c
> index 7d5204834ee2..3aa65f0f335e 100644
> --- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_dcb.c
> +++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_dcb.c
> @@ -471,7 +471,10 @@ static void cxgb4_getpgtccfg(struct net_device *dev, int tc,
>  		return;
>  	}
>  
> -	*bw_per = pcmd.u.dcb.pgrate.pgrate[*pgid];
> +	/* Valid values are: 0-7 */

How do you see it?

There are lines below that assume something different.
   477         /* prio_type is link strict */
   478         if (*pgid != 0xF)
   479                 *prio_type = 0x2;

> +	if (*pgid <= 7)
> +		*bw_per = pcmd.u.dcb.pgrate.pgrate[*pgid];

Why do you think that it is valid simply do not set *bw_per?

Thanks