netdev - Re: [RFC net] net/tls: clear SG markings on encryption error

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Date:   Fri, 22 Nov 2019 14:36:24 -0800
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     john.fastabend@...il.com, daniel@...earbox.net
Cc:     borisp@...lanox.com, aviadye@...lanox.com, netdev@...r.kernel.org,
        syzbot+df0d4ec12332661dd1f9@...kaller.appspotmail.com
Subject: Re: [RFC net] net/tls: clear SG markings on encryption error

On Fri, 22 Nov 2019 13:45:53 -0800, Jakub Kicinski wrote:
> Also there's at least one more bug in this piece of code, TLS 1.3
> can't assume there's at least one free SG entry.

And I don't see any place where the front and back of the SG circular
buffer are actually chained :( This:

static inline void sk_msg_init(struct sk_msg *msg)
{
	BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != MAX_MSG_FRAGS);
	memset(msg, 0, sizeof(*msg));
	sg_init_marker(msg->sg.data, MAX_MSG_FRAGS);
}

looks questionable as well, we shouldn't mark MAX_MSG_FRAGS as the end,
we don't know where the end is going to be..

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 6cb077b646a5..6c6ce6f90e7d 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -173,9 +173,8 @@ static inline void sk_msg_clear_meta(struct sk_msg *msg)
 
 static inline void sk_msg_init(struct sk_msg *msg)
 {
-       BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != MAX_MSG_FRAGS);
        memset(msg, 0, sizeof(*msg));
-       sg_init_marker(msg->sg.data, MAX_MSG_FRAGS);
+       sg_chain(msg->sg.data, ARRAY_SIZE(msg->sg.data), msg->sg.data);
 }
 
 static inline void sk_msg_xfer(struct sk_msg *dst, struct sk_msg *src,

Hm?