netdev - Re: [net] net/tls: fix corrupted data in recvmsg

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Date:   Sat, 14 Nov 2020 18:12:49 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vadim Fedorenko <vfedorenko@...ek.ru>
Cc:     Boris Pismenny <borisp@...dia.com>,
        Aviad Yehezkel <aviadye@...dia.com>, netdev@...r.kernel.org
Subject: Re: [net] net/tls: fix corrupted data in recvmsg

On Sat, 14 Nov 2020 07:09:42 +0300 Vadim Fedorenko wrote:
> If tcp socket has more data than Encrypted Handshake Message then
> tls_sw_recvmsg will try to decrypt next record instead of returning
> full control message to userspace as mentioned in comment. The next
> message - usually Application Data - gets corrupted because it uses
> zero copy for decryption that's why the data is not stored in skb
> for next iteration. Disable zero copy for this case.
> 
> Fixes: 692d7b5d1f91 ("tls: Fix recvmsg() to be able to peek across multiple records")
> Signed-off-by: Vadim Fedorenko <vfedorenko@...ek.ru>

Do you have some BPF in the mix?

I don't see how we would try to go past a non-data record otherwise, 
since the loop ends like this:

		if (tls_sw_advance_skb(sk, skb, chunk)) {
			/* Return full control message to
			 * userspace before trying to parse
			 * another message type
			 */
			msg->msg_flags |= MSG_EOR;
			if (ctx->control != TLS_RECORD_TYPE_DATA)
				goto recv_end;
		} else {
			break;
		}