Re: [PATCH net 1/3] ice: fix NULL pointer dereference in ice_update_vsi_tx_ring_stats()

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 15 Mar 2022 14:12:23 -0700 Tony Nguyen wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> 
> It is possible to do NULL pointer dereference in routine that updates
> Tx ring stats. Currently only stats and bytes are updated when ring

s/stats/packets/ ?

> pointer is valid, but later on ring is accessed to propagate gathered Tx
> stats onto VSI stats.
> 
> Change the existing logic to move to next ring when ring is NULL.
> 
> Fixes: e72bba21355d ("ice: split ice_ring onto Tx/Rx separate structs")
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
> Acked-by: Alexander Lobakin <alexandr.lobakin@intel.com>
> Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
> ---
>  drivers/net/ethernet/intel/ice/ice_main.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
> index 493942e910be..d4a7c39fd078 100644
> --- a/drivers/net/ethernet/intel/ice/ice_main.c
> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
> @@ -5962,8 +5962,9 @@ ice_update_vsi_tx_ring_stats(struct ice_vsi *vsi,
>  		u64 pkts = 0, bytes = 0;
>  
>  		ring = READ_ONCE(rings[i]);

Not really related to this patch but why is there a read_once() here?
Aren't stats read under rtnl_lock? What is this protecting against?

> -		if (ring)
> -			ice_fetch_u64_stats_per_ring(&ring->syncp, ring->stats, &pkts, &bytes);
> +		if (!ring)
> +			continue;
> +		ice_fetch_u64_stats_per_ring(&ring->syncp, ring->stats, &pkts, &bytes);