Re: [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: sta...@dpdk.org
Fixes: 4861cde46116 ("i40e: new poll mode driver")

Signed-off-by: Wei Zhao <wei.zh...@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;
  }