ip: reassembly: fix one possible use-after-free

When use the kv->v.memory_owner_thread_index as the index to get the
reass in pool, maybe this element is freed by the owner thread because
of timeout, too many fragments, and so on.

So we should check if do_handoff with kv->v.memory_owner_thread_index
before get the reass from pool.

Type: fix

Signed-off-by: Gao Feng <davidfgao@tencent.com>
Change-Id: Ie0f1dc368f86d0fd65292ca0c5e1908348015e09
(cherry picked from commit 9165e0365cc21575fd3e4a98be59317a839553f4)

2 files changed, 11 insertions, 10 deletions

diff --git a/src/vnet/ip/reass/ip4_full_reass.c b/src/vnet/ip/reass/ip4_full_reass.c
index a2d08a4909c..cebc6a0e965 100644
--- a/src/vnet/ip/reass/ip4_full_reass.c
+++ b/src/vnet/ip/reass/ip4_full_reass.c
@@ -459,15 +459,15 @@ again:
   if (!clib_bihash_search_16_8
       (&rm->hash, (clib_bihash_kv_16_8_t *) kv, (clib_bihash_kv_16_8_t *) kv))
     {
+      if (vm->thread_index != kv->v.memory_owner_thread_index)
+	{
+	  *do_handoff = 1;
+	  return NULL;
+	}
       reass =
 	pool_elt_at_index (rm->per_thread_data
 			   [kv->v.memory_owner_thread_index].pool,
 			   kv->v.reass_index);
-      if (vm->thread_index != reass->memory_owner_thread_index)
-	{
-	  *do_handoff = 1;
-	  return reass;
-	}
 
       if (now > reass->last_heard + rm->timeout)
 	{
diff --git a/src/vnet/ip/reass/ip6_full_reass.c b/src/vnet/ip/reass/ip6_full_reass.c
index 6848f59c65c..69ba452840e 100644
--- a/src/vnet/ip/reass/ip6_full_reass.c
+++ b/src/vnet/ip/reass/ip6_full_reass.c
@@ -471,16 +471,17 @@ again:
   if (!clib_bihash_search_48_8
       (&rm->hash, (clib_bihash_kv_48_8_t *) kv, (clib_bihash_kv_48_8_t *) kv))
     {
-      reass =
-	pool_elt_at_index (rm->per_thread_data
-			   [kv->v.memory_owner_thread_index].pool,
-			   kv->v.reass_index);
       if (vm->thread_index != kv->v.memory_owner_thread_index)
 	{
 	  *do_handoff = 1;
-	  return reass;
+	  return NULL;
 	}
 
+      reass =
+	pool_elt_at_index (rm->per_thread_data
+			   [kv->v.memory_owner_thread_index].pool,
+			   kv->v.reass_index);
+
       if (now > reass->last_heard + rm->timeout)
 	{
 	  ip6_full_reass_on_timeout (vm, node, rm, reass, icmp_bi);