From: Jiri Pirko <j...@mellanox.com>

The offending commit wrongly assumes 1:1 mapping between block and q.
However, there are multiple blocks for a single q for classful qdiscs.
Since the obscure tc_u_common sharing mechanism expects it to be shared
among a qdisc, fix it by storing q pointer in case the block is not
shared.

Reported-by: PaweĊ‚ Staszewski <pstaszew...@itcare.pl>
Reported-by: Cong Wang <xiyou.wangc...@gmail.com>
Fixes: 7fa9d974f3c2 ("net: sched: cls_u32: use block instead of q in 
tc_u_common")
Signed-off-by: Jiri Pirko <j...@mellanox.com>
---
 net/sched/cls_u32.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 6c7601a530e3..ed8b6a24b9e9 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -96,7 +96,7 @@ struct tc_u_hnode {
 
 struct tc_u_common {
        struct tc_u_hnode __rcu *hlist;
-       struct tcf_block        *block;
+       void                    *ptr;
        int                     refcnt;
        struct idr              handle_idr;
        struct hlist_node       hnode;
@@ -330,9 +330,25 @@ static struct hlist_head *tc_u_common_hash;
 #define U32_HASH_SHIFT 10
 #define U32_HASH_SIZE (1 << U32_HASH_SHIFT)
 
+static void *tc_u_common_ptr(const struct tcf_proto *tp)
+{
+       struct tcf_block *block = tp->chain->block;
+
+       /* The block sharing is currently supported only
+        * for classless qdiscs. In that case we use block
+        * for tc_u_common identification. In case the
+        * block is not shared, block->q is a valid pointer
+        * and we can use that. That works for classful qdiscs.
+        */
+       if (tcf_block_shared(block))
+               return block;
+       else
+               return block->q;
+}
+
 static unsigned int tc_u_hash(const struct tcf_proto *tp)
 {
-       return hash_ptr(tp->chain->block, U32_HASH_SHIFT);
+       return hash_ptr(tc_u_common_ptr(tp), U32_HASH_SHIFT);
 }
 
 static struct tc_u_common *tc_u_common_find(const struct tcf_proto *tp)
@@ -342,7 +358,7 @@ static struct tc_u_common *tc_u_common_find(const struct 
tcf_proto *tp)
 
        h = tc_u_hash(tp);
        hlist_for_each_entry(tc, &tc_u_common_hash[h], hnode) {
-               if (tc->block == tp->chain->block)
+               if (tc->ptr == tc_u_common_ptr(tp))
                        return tc;
        }
        return NULL;
@@ -371,7 +387,7 @@ static int u32_init(struct tcf_proto *tp)
                        kfree(root_ht);
                        return -ENOBUFS;
                }
-               tp_c->block = tp->chain->block;
+               tp_c->ptr = tc_u_common_ptr(tp);
                INIT_HLIST_NODE(&tp_c->hnode);
                idr_init(&tp_c->handle_idr);
 
-- 
2.14.3

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