[dpdk-dev] [PATCH] net/i40e: fix the security risk of wild pointer operation

[Jeff Guo]

hi, zhaowei

On 5/12/2020 11:19 PM, Wei Zhao wrote:
> In i40e PMD code of function i40e_res_pool_free(), if valid_entry is
> freed by "rte_free(valid_entry);" in the following code:
>
> if (prev != NULL) {
>   ........................
>
>     if (insert == 1) {
>       LIST_REMOVE(valid_entry, next);
>       rte_free(valid_entry);
>      } else {
>       rte_free(valid_entry);
>       insert = 1;
>      }
>    }
>
> then the following code for pool update may still use the wild pointer
> "valid_entry":
>
> " pool->num_free += valid_entry->len;
>    pool->num_alloc -= valid_entry>len;
> "
> it seems to be a security bug, we should avoid this risk.
>
> Cc: stable at dpdk.org
> Fixes: 4861cde46116 ("i40e: new poll mode driver")
>
> Signed-off-by: Wei Zhao <wei.zhao1 at intel.com>
> ---
>   drivers/net/i40e/i40e_ethdev.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/i40e/i40e_ethdev.c b/drivers/net/i40e/i40e_ethdev.c
> index 749d85f54..7f8ea5309 100644
> --- a/drivers/net/i40e/i40e_ethdev.c
> +++ b/drivers/net/i40e/i40e_ethdev.c
> @@ -4973,6 +4973,9 @@ i40e_res_pool_free(struct i40e_res_pool_info *pool,
>   	}
>   
>   	insert = 0;
> +	pool->num_free += valid_entry->len;
> +	pool->num_alloc -= valid_entry->len;
> +


Shouldn't the pool count update after the pool->free_list updated by 
"LIST_INSERT_HEAD(&pool->free_list, valid_entry, next)"?

If so, you could use a variable to restore  valid_entry->len at the 
begin and use it update pool count and other place.


>   	/* Try to merge with next one*/
>   	if (next != NULL) {
>   		/* Merge with next one */
> @@ -5010,9 +5013,6 @@ i40e_res_pool_free(struct i40e_res_pool_info *pool,
>   			LIST_INSERT_HEAD(&pool->free_list, valid_entry, next);
>   	}
>   
> -	pool->num_free += valid_entry->len;
> -	pool->num_alloc -= valid_entry->len;
> -
>   	return 0;
>   }
>