linux-kernel - Re: [PATCH] drivers/scsi/qla4xxx: use scnprintf() instead of snprintf()

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Date:   Wed, 20 Jan 2021 07:36:28 -0800
From:   James Bottomley <jejb@...ux.ibm.com>
To:     Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>, njavali@...vell.com
Cc:     mrangankar@...vell.com, GR-QLogic-Storage-Upstream@...vell.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/scsi/qla4xxx: use scnprintf() instead of
 snprintf()

On Wed, 2021-01-20 at 15:22 +0800, Jiapeng Zhong wrote:
> Fix the following coccicheck warning:
> 
> ./drivers/scsi/qla4xxx/ql4_attr.c: WARNING: use scnprintf or
> sprintf
> 
> The snprintf() function returns the number of characters which would
> have been printed if there were enough space, but the scnprintf()
> returns the number of characters which were actually printed.  If
> the buffer is not large enough, then using snprintf() would result
> in a read overflow and an information leak.
> 
> Reported-by: Abaci Robot<abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
> ---
>  drivers/scsi/qla4xxx/ql4_attr.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/scsi/qla4xxx/ql4_attr.c
> b/drivers/scsi/qla4xxx/ql4_attr.c
> index ec43528..1a16017 100644
> --- a/drivers/scsi/qla4xxx/ql4_attr.c
> +++ b/drivers/scsi/qla4xxx/ql4_attr.c
> @@ -170,7 +170,7 @@ void qla4_8xxx_free_sysfs_attr(struct
> scsi_qla_host *ha)
>  			char *buf)
>  {
>  	struct scsi_qla_host *ha = to_qla_host(class_to_shost(dev));
> -	return snprintf(buf, PAGE_SIZE, "%s\n", ha->serial_number);
> +	return scnprintf(buf, PAGE_SIZE, "%s\n", ha->serial_number);

This is the wrong ABI to be replacing anything sysfs with, it should be
sysfs_emit()

James