linux-kernel - [PATCH net] net/tls: fix tls_sk_proto

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Date:   Mon, 20 Jun 2022 12:35:08 +0800
From:   Ziyang Xuan <william.xuanziyang@...wei.com>
To:     <borisp@...dia.com>, <john.fastabend@...il.com>,
        <daniel@...earbox.net>, <kuba@...nel.org>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>
Subject: [PATCH net] net/tls: fix tls_sk_proto_close executed repeatedly

After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by
tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When
close the sock, tls_sk_proto_close() is called for sock->sk_prot->close
is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later
in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly
occurred. That will trigger the following bug.

=================================================================
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:tls_sk_proto_close+0xd8/0xaf0 net/tls/tls_main.c:306
Call Trace:
 <TASK>
 tls_sk_proto_close+0x356/0xaf0 net/tls/tls_main.c:329
 inet_release+0x12e/0x280 net/ipv4/af_inet.c:428
 __sock_release+0xcd/0x280 net/socket.c:650
 sock_close+0x18/0x20 net/socket.c:1365

Updating a proto which is same with sock->sk_prot is incorrect. Add proto
and sock->sk_prot equality check at the head of tls_update() to fix it.

Fixes: 95fa145479fb ("bpf: sockmap/tls, close can race with map free")
Reported-by: syzbot+29c3c12f3214b85ad081@...kaller.appspotmail.com
Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
---
 net/tls/tls_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index da176411c1b5..46bd5f26338b 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -921,6 +921,9 @@ static void tls_update(struct sock *sk, struct proto *p,
 {
 	struct tls_context *ctx;
 
+	if (sk->sk_prot == p)
+		return;
+
 	ctx = tls_get_ctx(sk);
 	if (likely(ctx)) {
 		ctx->sk_write_space = write_space;
-- 
2.25.1