[PATCH] net/tls: Fix sk_psock refcnt leak when in tls_data_ready()

[PATCH] net/tls: Fix sk_psock refcnt leak when in tls_data_ready()

[Xiyu Yang]

tls_data_ready() invokes sk_psock_get(), which returns a reference of
the specified sk_psock object to "psock" with increased refcnt.

When tls_data_ready() returns, local variable "psock" becomes invalid,
so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
tls_data_ready(). When "psock->ingress_msg" is empty but "psock" is not
NULL, the function forgets to decrease the refcnt increased by
sk_psock_get(), causing a refcnt leak.

Fix this issue by calling sk_psock_put() on all paths when "psock" is
not NULL.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
---
 net/tls/tls_sw.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index c98e602a1a2d..4eef5617e033 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -2081,8 +2081,9 @@ static void tls_data_ready(struct sock *sk)
 	strp_data_ready(&ctx->strp);
 
 	psock = sk_psock_get(sk);
-	if (psock && !list_empty(&psock->ingress_msg)) {
-		ctx->saved_data_ready(sk);
+	if (psock) {
+		if (!list_empty(&psock->ingress_msg))
+			ctx->saved_data_ready(sk);
 		sk_psock_put(sk, psock);
 	}
 }
-- 
2.7.4

Re: [PATCH] net/tls: Fix sk_psock refcnt leak when in tls_data_ready()

[David Miller]

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Date: Sat, 25 Apr 2020 21:10:23 +0800

> tls_data_ready() invokes sk_psock_get(), which returns a reference of
> the specified sk_psock object to "psock" with increased refcnt.
> 
> When tls_data_ready() returns, local variable "psock" becomes invalid,
> so the refcount should be decreased to keep refcount balanced.
> 
> The reference counting issue happens in one exception handling path of
> tls_data_ready(). When "psock->ingress_msg" is empty but "psock" is not
> NULL, the function forgets to decrease the refcnt increased by
> sk_psock_get(), causing a refcnt leak.
> 
> Fix this issue by calling sk_psock_put() on all paths when "psock" is
> not NULL.
> 
> Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>

Applied and queued up for -stable.