linux-kernel - Re: [PATCH net-next v10 08/16] tls: Inline do_tcp

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Message-ID: <20230803201212.1d5dd0f9@kernel.org>
Date:   Thu, 3 Aug 2023 20:12:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Tariq Toukan <ttoukan.linux@...il.com>
Cc:     David Howells <dhowells@...hat.com>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Chuck Lever III <chuck.lever@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Boris Pismenny <borisp@...dia.com>,
        John Fastabend <john.fastabend@...il.com>,
        Gal Pressman <gal@...dia.com>, ranro@...dia.com,
        samiram@...dia.com, drort@...dia.com,
        Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH net-next v10 08/16] tls: Inline do_tcp_sendpages()

On Thu, 3 Aug 2023 14:47:35 +0300 Tariq Toukan wrote:
> When applying this patch, repro disappears! :)
> Apparently it is related to the warning.
> Please go on and submit it.

I have no idea how. I found a different bug, staring at this code
for another hour. But I still don't get how we can avoid UaF on
a page by having the TCP take a ref on it rather than copy it.

If anything we should have 2 refs on any page in the sg, one because
it's on the sg, and another held by the re-tx handling.

So I'm afraid we're papering over something here :( We need to keep
digging.