[PATCH] net: sched: Fix qdisc_rate_table refcount leak when get tcf_block failed

The reference counting issue happens in one exception handling path of
cbq_change_class(). When failing to get tcf_block, the function forgets
to decrease the refcount of "rtab" increased by qdisc_put_rtab(),
causing a refcount leak.

Fix this issue by jumping to "failure" label when get tcf_block failed.

Signed-off-by: Xiyu Yang <redacted>
---
 net/sched/sch_cbq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index b79a7e27bb31..38a3a8394bbd 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c

@@ -1614,7 +1614,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t
 	err = tcf_block_get(&cl->block, &cl->filter_list, sch, extack);
 	if (err) {
 		kfree(cl);
-		return err;
+		goto failure;
 	}
 
 	if (tca[TCA_RATE]) {

-- 
2.7.4

On Sun, 29 Aug 2021 23:58:01 +0800 Xiyu Yang wrote:

The reference counting issue happens in one exception handling path of
cbq_change_class(). When failing to get tcf_block, the function forgets
to decrease the refcount of "rtab" increased by qdisc_put_rtab(),
causing a refcount leak.

Fix this issue by jumping to "failure" label when get tcf_block failed.

Signed-off-by: Xiyu Yang <redacted>

Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")

On Mon, Aug 30, 2021 at 11:05 AM Jakub Kicinski [off-list ref] wrote:

On Sun, 29 Aug 2021 23:58:01 +0800 Xiyu Yang wrote:

quoted

The reference counting issue happens in one exception handling path of
cbq_change_class(). When failing to get tcf_block, the function forgets
to decrease the refcount of "rtab" increased by qdisc_put_rtab(),
causing a refcount leak.

Fix this issue by jumping to "failure" label when get tcf_block failed.

Signed-off-by: Xiyu Yang <redacted>

Fixes: 6529eaba33f0 ("net: sched: introduce tcf block infractructure")

Reviewed-by: Cong Wang <redacted>

Thanks.

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Sun, 29 Aug 2021 23:58:01 +0800 you wrote:

The reference counting issue happens in one exception handling path of
cbq_change_class(). When failing to get tcf_block, the function forgets
to decrease the refcount of "rtab" increased by qdisc_put_rtab(),
causing a refcount leak.

Fix this issue by jumping to "failure" label when get tcf_block failed.

[...]

Here is the summary with links:
  - net: sched: Fix qdisc_rate_table refcount leak when get tcf_block failed
    https://git.kernel.org/netdev/net-next/c/c66070125837

You are awesome, thank you!
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