Re: [PATCH][next] netfilter: nftables: fix incorrect increment of loop counter

[Pablo Neira Ayuso]

Hi,

On Mon, Dec 14, 2020 at 11:40:15PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> 
> The intention of the err_expr cleanup path is to iterate over the
> allocated expr_array objects and free them, starting from i - 1 and
> working down to the start of the array. Currently the loop counter
> is being incremented instead of decremented and also the index i is
> being used instead of k, repeatedly destroying the same expr_array
> element.  Fix this by decrementing k and using k as the index into
> expr_array.
> 
> Addresses-Coverity: ("Infinite loop")
> Fixes: 8cfd9b0f8515 ("netfilter: nftables: generalize set expressions support")
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Reviewed-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>

@Jakub: Would you please take this one into net-next? Thanks!

> ---
>  net/netfilter/nf_tables_api.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 8d5aa0ac45f4..4186b1e52d58 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -5254,8 +5254,8 @@ static int nft_set_elem_expr_clone(const struct nft_ctx *ctx,
>  	return 0;
>  
>  err_expr:
> -	for (k = i - 1; k >= 0; k++)
> -		nft_expr_destroy(ctx, expr_array[i]);
> +	for (k = i - 1; k >= 0; k--)
> +		nft_expr_destroy(ctx, expr_array[k]);
>  
>  	return -ENOMEM;
>  }
> -- 
> 2.29.2
>