linux-kernel - Re: [PATCH v2] pstore: pstore_ftrace_seq

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Date:   Wed, 26 Feb 2020 10:40:47 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Joel Fernandes <joelaf@...gle.com>
Cc:     Vasily Averin <vvs@...tuozzo.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v2] pstore: pstore_ftrace_seq_next should increase
 position index

On Wed, Feb 26, 2020 at 01:36:45PM -0500, Joel Fernandes wrote:
> One thing I was not sure about is, if we move "pos" forward but still
> return NULL from next(), then does show() need to check if data is
> NULL? As below. Otherwise the suggested patch looks sane to me.
> 
> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
> index 7fbe8f0582205..e3e7370b1a34d 100644
> --- a/fs/pstore/inode.c
> +++ b/fs/pstore/inode.c
> @@ -101,6 +101,9 @@ static int pstore_ftrace_seq_show(struct seq_file
> *s, void *v)
>         struct pstore_ftrace_seq_data *data = v;
>         struct pstore_ftrace_record *rec;
> 
> +       if (!data)
> +               return 0;
> +
>         rec = (struct pstore_ftrace_record *)(ps->record->buf + data->off);
> 
>         seq_printf(s, "CPU:%d ts:%llu %08lx  %08lx  %ps <- %pS\n",

Ah, good point. I'm not sure, but it's worth checking I think. :)

-- 
Kees Cook