[NET_SCHED]: cls_basic: fix NULL pointer dereference

cls_basic doesn't allocate tp->root before it is linked into the
active classifier list, resulting in a NULL pointer dereference
when packets hit the classifier before its ->change function is
called.

Reported by Chris Madden <chris@reflexsecurity.com>

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 9 deletions

diff --git a/net/sched/cls_basic.c b/net/sched/cls_basic.c
index fad08e521c24..70fe36eb66a2 100644
--- a/net/sched/cls_basic.c
+++ b/net/sched/cls_basic.c
@@ -81,6 +81,13 @@ static void basic_put(struct tcf_proto *tp, unsigned long f)
 
 static int basic_init(struct tcf_proto *tp)
 {
+        struct basic_head *head;
+
+        head = kzalloc(sizeof(*head), GFP_KERNEL);
+        if (head == NULL)
+                return -ENOBUFS;
+        INIT_LIST_HEAD(&head->flist);
+        tp->root = head;
         return 0;
 }
 
@@ -176,15 +183,6 @@ static int basic_change(struct tcf_proto *tp, unsigned long base, u32 handle,
         }
 
         err = -ENOBUFS;
-        if (head == NULL) {
-                head = kzalloc(sizeof(*head), GFP_KERNEL);
-                if (head == NULL)
-                        goto errout;
-
-                INIT_LIST_HEAD(&head->flist);
-                tp->root = head;
-        }
-
         f = kzalloc(sizeof(*f), GFP_KERNEL);
         if (f == NULL)
                 goto errout;