Re: [PATCH net-next] sfc: fix use-after-free in efx_tc_flower_record_encap_match()

[Simon Horman <simon.horman@corigine.com>]

On Fri, May 12, 2023 at 04:35:58PM +0100, edward.cree@amd.com wrote:
> From: Edward Cree <ecree.xilinx@gmail.com>
> 
> When writing error messages to extack for pseudo collisions, we can't
>  use encap->type as encap has already been freed.  Fortunately the
>  same value is stored in local variable em_type, so use that instead.
> 
> Fixes: 3c9561c0a5b9 ("sfc: support TC decap rules matching on enc_ip_tos")
> Reported-by: Simon Horman <simon.horman@corigine.com>
> Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>

Thanks,

Reviewed-by: Simon Horman <simon.horman@corigine.com>

> ---
>  drivers/net/ethernet/sfc/tc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sfc/tc.c b/drivers/net/ethernet/sfc/tc.c
> index da684b4b7211..6dfbdb39f2fe 100644
> --- a/drivers/net/ethernet/sfc/tc.c
> +++ b/drivers/net/ethernet/sfc/tc.c
> @@ -504,7 +504,7 @@ static int efx_tc_flower_record_encap_match(struct efx_nic *efx,
>  			if (em_type != EFX_TC_EM_PSEUDO_MASK) {
>  				NL_SET_ERR_MSG_FMT_MOD(extack,
>  						       "%s encap match conflicts with existing pseudo(MASK) entry",
> -						       encap->type ? "Pseudo" : "Direct");
> +						       em_type ? "Pseudo" : "Direct");
>  				return -EEXIST;
>  			}
>  			if (child_ip_tos_mask != old->child_ip_tos_mask) {
> @@ -525,7 +525,7 @@ static int efx_tc_flower_record_encap_match(struct efx_nic *efx,
>  		default: /* Unrecognised pseudo-type.  Just say no */
>  			NL_SET_ERR_MSG_FMT_MOD(extack,
>  					       "%s encap match conflicts with existing pseudo(%d) entry",
> -					       encap->type ? "Pseudo" : "Direct",
> +					       em_type ? "Pseudo" : "Direct",
>  					       old->type);
>  			return -EEXIST;
>  		}
>