linux-kernel - Re: [PATCH v5 2/6] net/handshake: Define handshake_sk_destruct

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Message-ID: <49bbe54a-4b55-48a7-bfb4-30a222cb7d4f@oracle.com>
Date: Wed, 12 Nov 2025 10:47:10 -0500
From: Chuck Lever <chuck.lever@...cle.com>
To: alistair23@...il.com, hare@...nel.org,
        kernel-tls-handshake@...ts.linux.dev, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-nfs@...r.kernel.org
Cc: kbusch@...nel.org, axboe@...nel.dk, hch@....de, sagi@...mberg.me,
        kch@...dia.com, hare@...e.de,
        Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v5 2/6] net/handshake: Define handshake_sk_destruct_req

On 11/11/25 11:27 PM, alistair23@...il.com wrote:
> From: Alistair Francis <alistair.francis@....com>
> 
> Define a `handshake_sk_destruct_req()` function to allow the destruction
> of the handshake req.
> 
> This is required to avoid hash conflicts when handshake_req_hash_add()
> is called as part of submitting the KeyUpdate request.
> 
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> Reviewed-by: Hannes Reinecke <hare@...e.de>
> ---
> v5:
>  - No change
> v4:
>  - No change
> v3:
>  - New patch
> 
>  net/handshake/request.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/net/handshake/request.c b/net/handshake/request.c
> index 274d2c89b6b2..0d1c91c80478 100644
> --- a/net/handshake/request.c
> +++ b/net/handshake/request.c
> @@ -98,6 +98,22 @@ static void handshake_sk_destruct(struct sock *sk)
>  		sk_destruct(sk);
>  }
>  
> +/**
> + * handshake_sk_destruct_req - destroy an existing request
> + * @sk: socket on which there is an existing request

Generally the kdoc style is unnecessary for static helper functions,
especially functions with only a single caller.

This all looks so much like handshake_sk_destruct(). Consider
eliminating the code duplication by splitting that function into a
couple of helpers instead of adding this one.

> + */
> +static void handshake_sk_destruct_req(struct sock *sk)

Because this function is static, I imagine that the compiler will
bark about the addition of an unused function. Perhaps it would
be better to combine 2/6 and 3/6.

That would also make it easier for reviewers to check the resource
accounting issues mentioned below.

> +{
> +	struct handshake_req *req;
> +
> +	req = handshake_req_hash_lookup(sk);
> +	if (!req)
> +		return;
> +
> +	trace_handshake_destruct(sock_net(sk), req, sk);

Wondering if this function needs to preserve the socket's destructor
callback chain like so:

+	void (sk_destruct)(struct sock sk);

  ...

+	sk_destruct = req->hr_odestruct;
+	sk->sk_destruct = sk_destruct;

then:

> +	handshake_req_destroy(req);

Because of the current code organization and patch ordering, it's
difficult to confirm that sock_put() isn't necessary here.

> +}
> +
>  /**
>   * handshake_req_alloc - Allocate a handshake request
>   * @proto: security protocol

There's no synchronization preventing concurrent handshake_req_cancel()
calls from accessing the request after it's freed during handshake
completion. That is one reason why handshake_complete() leaves completed
requests in the hash.

So I'm thinking that removing requests like this is not going to work
out. Would it work better if handshake_req_hash_add() could recognize
that a KeyUpdate is going on, and allow replacement of a hashed
request? I haven't thought that through.

As always, please double-check my questions and assumptions before
revising this patch!

-- 
Chuck Lever