linux-kernel - [PATCH] net: tls: enable __GFP_ZERO upon tls

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Message-ID: <c16e9ab9-13e0-b911-e33a-c9ae81e93a8d@I-love.SAKURA.ne.jp>
Date:   Wed, 28 Jun 2023 22:48:01 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Boris Pismenny <borisp@...dia.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     glider@...gle.com, herbert@...dor.apana.org.au,
        linux-crypto@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+828dfc12440b4f6f305d@...kaller.appspotmail.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Aviad Yehezkel <aviadye@...dia.com>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] net: tls: enable __GFP_ZERO upon tls_init()

syzbot is reporting uninit-value at aes_encrypt(), for block cipher assumes
that bytes to encrypt/decrypt is multiple of block size for that cipher but
tls_alloc_encrypted_msg() is not initializing padding bytes when
required_size is not multiple of block cipher's block size.

In order to make sure that padding bytes are automatically initialized,
enable __GFP_ZERO flag when setsockopt(SOL_TCP, TCP_ULP, "tls") is called.

Reported-by: syzbot <syzbot+828dfc12440b4f6f305d@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=828dfc12440b4f6f305d
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
According to C reproducer, this problem happens when bpf_exec_tx_verdict() is
called with lower 4 bits of required_size being 0001 and does not happen when
being 0100. Thus, I assumed that this problem is caused by lack of initializing
padding bytes.
But I couldn't figure out why KMSAN reports this problem when bpf_exec_tx_verdict()
is called with lower 4 bits of required_size being 0001 for the second time and
does not report this problem when bpf_exec_tx_verdict() is called with lower
4 bits of required_size being 0001 for the first time. More deeper problem exists?
KMSAN reporting this problem when accessing u64 relevant?

 net/tls/tls_main.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index f2e7302a4d96..cd5366966864 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -1025,6 +1025,7 @@ static int tls_init(struct sock *sk)
 	struct tls_context *ctx;
 	int rc = 0;
 
+	sk->sk_allocation |= __GFP_ZERO;
 	tls_build_proto(sk);
 
 #ifdef CONFIG_TLS_TOE
-- 
2.34.1