linux-kernel - Re: [RFC 2/5] ia64/sn/hwperf: use seq_open

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Date:   Fri, 2 Mar 2018 09:22:57 +0100
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/5] ia64/sn/hwperf: use seq_open_data

On 2 March 2018 at 00:37, Rasmus Villemoes <linux@...musvillemoes.dk> wrote:
> This code should check the return value of seq_open(); if it failed,
> file->private_data is NULL. But we can avoid the issue entirely and
> simplify the code by letting seq_open_data() set the ->private member
> to objbuf.
>
>         if ((e = sn_hwperf_enum_objects(&nobj, &objbuf)) == 0) {
> -               e = seq_open(file, &sn_topology_seq_ops);
> -               seq = file->private_data;
> -               seq->private = objbuf;
> +               e = seq_open_data(file, &sn_topology_seq_ops, objbuf);
>         }

Well, this turns a NULL deref into a resource leak; we still need to
add a check of the return value and vfree(objbuf) on failure.

Rasmus