linux-kernel - Re: [PATCH 20/22] pstore: %pF is only for function pointers

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Message-ID: <CAGXu5j+OAdiv=D_pYeGnp-JSKthkibEp=aRYmuPotc9G+J3WiA@mail.gmail.com>
Date:	Tue, 16 Jun 2015 15:02:50 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Anton Vorontsov <anton@...msg.org>
Cc:	trivial@...nel.org, LKML <linux-kernel@...r.kernel.org>,
	Colin Cross <ccross@...roid.com>,
	Tony Luck <tony.luck@...el.com>,
	Scott Wood <scottwood@...escale.com>
Subject: Re: [PATCH 20/22] pstore: %pF is only for function pointers

On Wed, Mar 11, 2015 at 8:13 PM, Scott Wood <scottwood@...escale.com> wrote:
> Use %pS for actual addresses, otherwise you'll get bad output
> on arches like ppc64 where %pF expects a function descriptor.
>
> Signed-off-by: Scott Wood <scottwood@...escale.com>
> Cc: Anton Vorontsov <anton@...msg.org>
> Cc: Colin Cross <ccross@...roid.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Tony Luck <tony.luck@...el.com>
> ---
>  fs/pstore/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
> index b32ce53..f8a5bfe 100644
> --- a/fs/pstore/inode.c
> +++ b/fs/pstore/inode.c
> @@ -107,7 +107,7 @@ static int pstore_ftrace_seq_show(struct seq_file *s, void *v)
>         struct pstore_ftrace_seq_data *data = v;
>         struct pstore_ftrace_record *rec = (void *)(ps->data + data->off);
>
> -       seq_printf(s, "%d %08lx  %08lx  %pf <- %pF\n",
> +       seq_printf(s, "%d %08lx  %08lx  %ps <- %pS\n",
>                 pstore_ftrace_decode_cpu(rec), rec->ip, rec->parent_ip,
>                 (void *)rec->ip, (void *)rec->parent_ip);
>
> --
> 2.1.0
>

Anton, does this look okay to you? (i.e. switching from function
pointer to direct pointer?) vsprintf docs say:
 * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
 * function pointers are really function descriptors, which contain a
 * pointer to the real address.

So this seems correct to me.

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook
Chrome OS Security
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