Subject: [PATCH 18/21] net: cls_flower: Remove filter from mask before freeing it

From: Petr Machata <[email-masked]>
Date: Mon, 4 Feb 2019 14:50:38 +0000

[ Upstream commit c1f7e02979edd7a3a3e69fe04be60b1d650dc8a7 ]

In fl_change(), when adding a new rule (i.e. fold == NULL), a driver may
reject the new rule, for example due to resource exhaustion. By that
point, the new rule was already assigned a mask, and it was added to
that mask's hash table. The clean-up path that's invoked as a result of
the rejection however neglects to undo the hash table addition, and
proceeds to free the new rule, thus leaving a dangling pointer in the
hash table.

Fix by removing fnew from the mask's hash table before it is freed.

Fixes: 35cc3cefc4de ("net/sched: cls_flower: Reject duplicated rules also under skip_sw")
Signed-off-by: Petr Machata <[email-masked]>
Acked-by: Jiri Pirko <[email-masked]>
Reviewed-by: Ido Schimmel <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/sched/cls_flower.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index 45bc2b72dc1c..2f64e3538127 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1257,7 +1257,7 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	if (!tc_skip_hw(fnew->flags)) {
 		err = fl_hw_replace_filter(tp, fnew, extack);
 		if (err)
-			goto errout_mask;
+			goto errout_mask_ht;
 	}
 
 	if (!tc_in_hw(fnew->flags))
@@ -1287,6 +1287,10 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
 	kfree(mask);
 	return 0;
 
+errout_mask_ht:
+	rhashtable_remove_fast(&fnew->mask->ht, &fnew->ht_node,
+			       fnew->mask->filter_ht_params);
+
 errout_mask:
 	fl_mask_put(head, fnew->mask, false);
 
-- 
2.20.1