linux-kernel - Re: [PATCH] relay: When unsigned ret cannot store a negative value

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Date:	Tue, 2 Dec 2008 14:10:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	roel kluin <roel.kluin@...il.com>
Cc:	linux-kernel@...r.kernel.org, Tom Zanussi <zanussi@...ibm.com>,
	Tom Zanussi <zanussi@...cast.net>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH] relay: When unsigned ret cannot store a negative value

On Sat, 29 Nov 2008 10:38:06 -0500
roel kluin <roel.kluin@...il.com> wrote:

> When unsigned ret cannot store a negative value
> 
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> UNTESTED! is this the way to go?
> 
> diff --git a/kernel/relay.c b/kernel/relay.c
> index 32b0bef..c9d62e5 100644
> --- a/kernel/relay.c
> +++ b/kernel/relay.c
> @@ -1220,7 +1220,8 @@ static int subbuf_splice_actor(struct file *in,
>  			       unsigned int flags,
>  			       int *nonpad_ret)
>  {
> -	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
> +	unsigned int pidx, poff, total_len, subbuf_pages, nr_pages;
> +	ssize_t ret;
>  	struct rchan_buf *rbuf = in->private_data;
>  	unsigned int subbuf_size = rbuf->chan->subbuf_size;
>  	uint64_t pos = (uint64_t) *ppos;
> @@ -1289,7 +1290,8 @@ static int subbuf_splice_actor(struct file *in,
>  	if (!spd.nr_pages)
>  		return 0;
>  
> -	ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
> +	ret = splice_to_pipe(pipe, &spd);
> +	*nonpad_ret = ret;
>  	if (ret < 0 || ret < total_len)
>  		return ret;
>  

Yeah, this code needs help.  subbuf_splice_actor() returns `int', but
carefully calculates and returns an unsigned type.

I suspect that quite a bit of code in there (including
relay_file_splice_read()) should be gone through and have its choice of
types reviewed and fixed.  Probably by converting things to ssize_t.


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