linux-kernel - RE: [PATCH] ima: Replace two seq_printf() calls by seq_puts() in ima_show_template_data

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Message-ID: <d94bfdb9d53b46059787b9bdd10c5919@AcuMS.aculab.com>
Date:   Wed, 3 Jul 2019 09:16:44 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Markus Elfring' <Markus.Elfring@....de>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        "Serge E. Hallyn" <serge@...lyn.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: RE: [PATCH] ima: Replace two seq_printf() calls by seq_puts() in
 ima_show_template_data_ascii()

From:  Markus Elfring
> Sent: 02 July 2019 20:01
> 
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Tue, 2 Jul 2019 20:52:21 +0200
> 
> Two strings which did not contain a data format specification should be put
> into a sequence. Thus use the corresponding function “seq_puts”.
> 
> This issue was detected by using the Coccinelle software.

The two calls are almost certainly absolutely equivalent.
So this is probably just a minor performance improvement in a code
path where it really doesn't matter.

> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>  security/integrity/ima/ima_template_lib.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
> index 9fe0ef7f91e2..05636e9b19b1 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -74,7 +74,7 @@ static void ima_show_template_data_ascii(struct seq_file *m,
>  	case DATA_FMT_DIGEST_WITH_ALGO:
>  		buf_ptr = strnchr(field_data->data, buflen, ':');
>  		if (buf_ptr != field_data->data)
> -			seq_printf(m, "%s", field_data->data);
> +			seq_puts(m, field_data->data);
> 
>  		/* skip ':' and '\0' */
>  		buf_ptr += 2;

That code looks highly suspect!
It uses a bounded scan then assumes a '\0' terminated string.
It then adds 2 to a potentially NULL pointer.

About typical for 'security' code :-)

	David

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