[PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core

* [PATCH] net/l2tp: Fix reference count leak in l2tp_udp_recv_core
@ 2021-09-09  4:32 Xiyu Yang
  2021-09-09  9:01 ` Tom Parkin
  2021-09-09 10:10 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 4+ messages in thread
From: Xiyu Yang @ 2021-09-09  4:32 UTC (permalink / raw)
  To: David S. Miller, Jakub Kicinski, Cong Wang, Randy Dunlap,
	Tom Parkin, Xin Xiong, Gong, Sishuai, Matthias Schiffer,
	Xiyu Yang, Bhaskar Chowdhury, netdev, linux-kernel
  Cc: yuanxzhang, Xin Tan

The reference count leak issue may take place in an error handling
path. If both conditions of tunnel->version == L2TP_HDR_VER_3 and the
return value of l2tp_v3_ensure_opt_in_linear is nonzero, the function
would directly jump to label invalid, without decrementing the reference
count of the l2tp_session object session increased earlier by
l2tp_tunnel_get_session(). This may result in refcount leaks.

Fix this issue by decrease the reference count before jumping to the
label invalid.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Xiong <xiongx18@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 net/l2tp/l2tp_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 53486b162f01..93271a2632b8 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -869,8 +869,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 	}
 
 	if (tunnel->version == L2TP_HDR_VER_3 &&
-	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr)) {
+		l2tp_session_dec_refcount(session);
 		goto invalid;
+	}
 
 	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 	l2tp_session_dec_refcount(session);
-- 
2.7.4


^ permalink raw reply related	[flat|nested] 4+ messages in thread