[PATCH 5.15 039/124] net/sched: cls_u32: fix possible leak in u32_init_knode()

Greg Kroah-Hartman
2022-04-26T09:08:53Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit ec5b0f605b105457f257f2870acad4a5d463984b ]

While investigating a related syzbot report,
I found that whenever call to tcf_exts_init()
from u32_init_knode() is failing, we end up
with an elevated refcount on ht->refcnt

To avoid that, only increase the refcount after
all possible errors have been evaluated.

Fixes: b9a24bb76bf6 ("net_sched: properly handle failure case of tcf_exts_init()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/cls_u32.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 81f933ebee05..5d30db0d7157 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -814,10 +814,6 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp,
new->flags = n->flags;
RCU_INIT_POINTER(new->ht_down, ht);

- /* bump reference count as long as we hold pointer to structure */
- if (ht)
- ht->refcnt++;
-
#ifdef CONFIG_CLS_U32_PERF
/* Statistics may be incremented by readers during update
* so we must keep them in tact. When the node is later destroyed
@@ -839,6 +835,10 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp,
return NULL;
}

+ /* bump reference count as long as we hold pointer to structure */
+ if (ht)
+ ht->refcnt++;
+
return new;
}

--
2.35.1