net: possible use after free in dst_release

dst_release should not access dst->flags after decrementing __refcnt to 0. The dst_entry may be in dst_busy_list and dst_gc_task may dst_destroy it before dst_release gets a chance to access dst->flags. Fixes: d69bbf8 ("net: fix a race in dst_release()") Fixes: 27b75c9 ("net: avoid RCU for NOCACHE dst") Signed-off-by: Francesco Ruggeri <[email protected]> Acked-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
CamonZ · Jan 6, 2016 · 07a5d38 · 07a5d38
1 parent 73c20a8
commit 07a5d38
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/net/core/dst.c b/net/core/dst.c
@@ -301,12 +301,13 @@ void dst_release(struct dst_entry *dst)
 {
 	if (dst) {
 		int newrefcnt;
+		unsigned short nocache = dst->flags & DST_NOCACHE;
 
 		newrefcnt = atomic_dec_return(&dst->__refcnt);
 		if (unlikely(newrefcnt < 0))
 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
 					     __func__, dst, newrefcnt);
-		if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
+		if (!newrefcnt && unlikely(nocache))
 			call_rcu(&dst->rcu_head, dst_destroy_rcu);
 	}
 }