netdev - Re: [bpf PATCH 6/9] bpf: sockmap/tls, tls_sw can create a plaintext buf

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Message-ID: <B265C993-B266-4CC7-B32A-C877667C545A@flugsvamp.com>
Date:   Thu, 09 Jan 2020 15:04:40 -0800
From:   "Jonathan Lemon" <jlemon@...gsvamp.com>
To:     "John Fastabend" <john.fastabend@...il.com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net
Subject: Re: [bpf PATCH 6/9] bpf: sockmap/tls, tls_sw can create a plaintext
 buf > encrypt buf

On 8 Jan 2020, at 13:15, John Fastabend wrote:

> It is possible to build a plaintext buffer using push helper that is larger
> than the allocated encrypt buffer. When this record is pushed to crypto
> layers this can result in a NULL pointer dereference because the crypto
> API expects the encrypt buffer is large enough to fit the plaintext
> buffer.
>
> To resolve catch the cases this can happen and split the buffer into two
> records to send individually. Unfortunately, there is still one case to
> handle where the split creates a zero sized buffer. In this case we merge
> the buffers and unmark the split. This happens when apply is zero and user
> pushed data beyond encrypt buffer. This fixes the original case as well
> because the split allocated an encrypt buffer larger than the plaintext
> buffer and the merge simply moves the pointers around so we now have
> a reference to the new (larger) encrypt buffer.
>
> Perhaps its not ideal but it seems the best solution for a fixes branch
> and avoids handling these two cases, (a) apply that needs split and (b)
> non apply case. The are edge cases anyways so optimizing them seems not
> necessary unless someone wants later in next branches.
>
> Fixes: d3b18ad31f93d ("tls: add bpf support to sk_msg handling")
> Signed-off-by: John Fastabend <john.fastabend@...il.com>

Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>