linux-kernel - Re: [PATCH] target: iscsi: iscsi_target_tpg.c: Cleaning up possible size overwriting in conjunction with sprintf

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Date:	Sun, 12 Oct 2014 11:18:43 -0700
From:	Joe Perches <joe@...ches.com>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
Cc:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	Sagi Grimberg <sagig@...lanox.com>,
	Andy Grover <agrover@...hat.com>,
	Thomas Glanzmann <thomas@...nzmann.de>,
	Christophe Vu-Brugier <cvubrugier@...oo.fr>,
	linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] target: iscsi: iscsi_target_tpg.c:  Cleaning up
 possible size overwriting in conjunction with sprintf

On Sun, 2014-10-12 at 19:55 +0200, Rickard Strandqvist wrote:
> Changed same snprintf and sprintf to strlcpy and strlcat.
> This will guarantee that the string size is not overwritten,
> and they are significantly faster than sprintf also.

I don't disagree with the change, but I think the changelog is
misleading.

strlcpy(ptr, ...) then strlcat(ptr, ...) does not use the known
length of the first copied string and is generally not faster than
ptr += snprintf(ptr, ...) then sprintf(ptr,...)

And a couple slightly unrelated bits:

> diff --git a/drivers/target/iscsi/iscsi_target_tpg.c b/drivers/target/iscsi/iscsi_target_tpg.c
> index c3cb5c1..6fc8bfe 100644
> --- a/drivers/target/iscsi/iscsi_target_tpg.c
> +++ b/drivers/target/iscsi/iscsi_target_tpg.c
> @@ -608,7 +608,6 @@ int iscsit_tpg_set_initiator_node_queue_depth(
>  int iscsit_ta_authentication(struct iscsi_portal_group *tpg, u32 authentication)

This function could be made static and the prototype removed from
the .h file if it is moved above its one caller in this file.

>  {
>  	unsigned char buf1[256], buf2[256], *none = NULL;

Moderately large stack use here.


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