net: cls_flower: Remove filter from mask before freeing it [Linux 5.0]

net: cls_flower: Remove filter from mask before freeing it [Linux 5.0]

This Linux kernel change "net: cls_flower: Remove filter from mask before freeing it" is included in the Linux 5.0 release. This change is authored by Petr Machata <petrm [at] mellanox.com> on Mon Feb 4 14:50:38 2019 +0000. The commit for this change in Linux stable tree is c1f7e02 (patch).

net: cls_flower: Remove filter from mask before freeing it

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 protected]>
Acked-by: Jiri Pirko <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 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 f6aa57f..12ca9d1 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1371,7 +1371,7 @@ 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))
@@ -1401,6 +1401,10 @@ 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);

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