tcf_chain_destroy() is called by tcf_block_put() and tcf_chain_put().
tcf_chain_put() is refcn'ed and paired with tcf_chain_get(),
but tcf_block_put() is not, it should be paired with tcf_block_get()
and we still need to decrease the refcnt. However, tcf_block_put()
is special, it stores the chains too, we have to detach them if
it is not the last user.
What's more, index 0 is not special at all, it should be treated
like other chains. This also makes the code more readable.
Fixes: 744a4cf63e52 ("net: sched: fix use after free when tcf_chain_destroy is
called multiple times")
Reported-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Cc: Jiri Pirko <j...@mellanox.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/sched/cls_api.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 6c5ea84d2682..c6d25b29bcd4 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -213,17 +213,17 @@ static void tcf_chain_flush(struct tcf_chain *chain)
}
}
-static void tcf_chain_destroy(struct tcf_chain *chain)
+static void tcf_chain_detach(struct tcf_chain *chain)
{
/* May be already removed from the list by the previous call. */
if (!list_empty(&chain->list))
list_del_init(&chain->list);
+}
- /* There might still be a reference held when we got here from
- * tcf_block_put. Wait for the user to drop reference before free.
- */
- if (!chain->refcnt)
- kfree(chain);
+static void tcf_chain_destroy(struct tcf_chain *chain)
+{
+ tcf_chain_detach(chain);
+ kfree(chain);
}
struct tcf_chain *tcf_chain_get(struct tcf_block *block, u32 chain_index,
@@ -246,10 +246,7 @@ EXPORT_SYMBOL(tcf_chain_get);
void tcf_chain_put(struct tcf_chain *chain)
{
- /* Destroy unused chain, with exception of chain 0, which is the
- * default one and has to be always present.
- */
- if (--chain->refcnt == 0 && !chain->filter_chain && chain->index != 0)
+ if (--chain->refcnt == 0)
tcf_chain_destroy(chain);
}
EXPORT_SYMBOL(tcf_chain_put);
@@ -296,8 +293,11 @@ void tcf_block_put(struct tcf_block *block)
list_for_each_entry_safe(chain, tmp, &block->chain_list, list) {
tcf_chain_flush(chain);
- tcf_chain_destroy(chain);
+ tcf_chain_put(chain);
}
+ /* If tc actions still hold the chain, just detach it. */
+ list_for_each_entry_safe(chain, tmp, &block->chain_list, list)
+ tcf_chain_detach(chain);
kfree(block);
}
EXPORT_SYMBOL(tcf_block_put);
--
2.13.0
