Re: [PATCH 1/3] net: ethernet: bcmasp: fix possible OOB write in bcmasp_netfilt_get_all_active()

[Paolo Abeni]

On Wed, 2023-09-06 at 17:21 +0800, Hangyu Hua wrote:
> rule_locs is allocated in ethtool_get_rxnfc and the size is determined by
> rule_cnt from user space. So rule_cnt needs to be check before using
> rule_locs to avoid OOB writing or NULL pointer dereference.
> 
> Fixes: c5d511c49587 ("net: bcmasp: Add support for wake on net filters")
> Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> ---
>  drivers/net/ethernet/broadcom/asp2/bcmasp.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/asp2/bcmasp.c b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> index d63d321f3e7b..4df2ca871af8 100644
> --- a/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> +++ b/drivers/net/ethernet/broadcom/asp2/bcmasp.c
> @@ -535,6 +535,9 @@ void bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
>  	int j = 0, i;
>  
>  	for (i = 0; i < NUM_NET_FILTERS; i++) {
> +		if (j == *rule_cnt)
> +			break;

Side note: it's a bit unfortunate/confusing that the drivers can
arbitrary return  -EMSGSIZE or silently truncate the list. I think it
would be clearer if we could stick to single behavior - and I'll vote
for -EMSGSIZE.

Cheers,

Paolo