net: sched: cls_u32: mark root hnode explicitly

... and produce consistent error on attempt to delete such.
Existing check in u32_delete() is inconsistent - after

tc qdisc add dev eth0 ingress
tc filter add dev eth0 parent ffff: protocol ip prio 100 handle 1: u32 \
divisor 1
tc filter add dev eth0 parent ffff: protocol ip prio 200 handle 2: u32 \
divisor 1

both

tc filter delete dev eth0 parent ffff: protocol ip prio 100 handle 801: u32

and

tc filter delete dev eth0 parent ffff: protocol ip prio 100 handle 800: u32

will fail (at least with refcounting fixes), but the former will complain
about an attempt to remove a busy table, while the latter will recognize
it as root and yield "Not allowed to delete root node" instead.

The problem with the existing check is that several tcf_proto instances
might share the same tp->data and handle-to-hnode lookup will be the same
for all of them. So comparing an hnode to be deleted with tp->root won't
catch the case when one tp is used to try deleting the root of another.
Solution is trivial - mark the root hnodes explicitly upon allocation and
check for that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index f218ccf..622f465 100644 (file)
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -84,6 +84,7 @@ struct tc_u_hnode {
        int                     refcnt;
        unsigned int            divisor;
        struct idr              handle_idr;
+       bool                    is_root;
        struct rcu_head         rcu;
        u32                     flags;
        /* The 'ht' field MUST be the last field in structure to allow for
@@ -377,6 +378,7 @@ static int u32_init(struct tcf_proto *tp)
        root_ht->refcnt++;
        root_ht->handle = tp_c ? gen_new_htid(tp_c, root_ht) : 0x80000000;
        root_ht->prio = tp->prio;
+       root_ht->is_root = true;
        idr_init(&root_ht->handle_idr);
 
        if (tp_c == NULL) {
@@ -692,7 +694,7 @@ static int u32_delete(struct tcf_proto *tp, void *arg, bool *last,
                goto out;
        }
 
-       if (root_ht == ht) {
+       if (ht->is_root) {
                NL_SET_ERR_MSG_MOD(extack, "Not allowed to delete root node");
                return -EINVAL;
        }