linux-hardening - Re: [PATCH v2] scsi: hpsa: Replace deprecated strncpy() with strscpy()

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Message-ID: <065b6317-8da8-42ec-8084-1a5058c0798a@acm.org>
Date: Thu, 13 Feb 2025 12:34:55 -0800
From: Bart Van Assche <bvanassche@....org>
To: Thorsten Blum <thorsten.blum@...ux.dev>,
 Don Brace <don.brace@...rochip.com>,
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
 "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-hardening@...r.kernel.org, storagedev@...rochip.com,
 linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] scsi: hpsa: Replace deprecated strncpy() with
 strscpy()

On 2/13/25 11:53 AM, Thorsten Blum wrote:
> diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
> index 84d8de07b7ae..c7ebae24b09f 100644
> --- a/drivers/scsi/hpsa.c
> +++ b/drivers/scsi/hpsa.c
> @@ -460,9 +460,8 @@ static ssize_t host_store_hp_ssd_smart_path_status(struct device *dev,
>   
>   	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
>   		return -EACCES;
> -	len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
> -	strncpy(tmpbuf, buf, len);
> -	tmpbuf[len] = '\0';
> +	len = min(count + 1, sizeof(tmpbuf));
> +	strscpy(tmpbuf, buf, len);
>   	if (sscanf(tmpbuf, "%d", &status) != 1)
>   		return -EINVAL;
>   	h = shost_to_hba(shost);
> @@ -484,9 +483,8 @@ static ssize_t host_store_raid_offload_debug(struct device *dev,
>   
>   	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
>   		return -EACCES;
> -	len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
> -	strncpy(tmpbuf, buf, len);
> -	tmpbuf[len] = '\0';
> +	len = min(count + 1, sizeof(tmpbuf));
> +	strscpy(tmpbuf, buf, len);
>   	if (sscanf(tmpbuf, "%d", &debug_level) != 1)
>   		return -EINVAL;
>   	if (debug_level < 0)

Something I should have noticed earlier: this code occurs inside sysfs
write callbacks. The strings passed to sysfs write callbacks are
0-terminated. Hence, 'buf' can be passed directly to sscanf() and
tmpbuf[] can be removed. From kernfs_fop_write_iter() in fs/kernfs.c:

	buf[len] = '\0';	/* guarantee string termination */

Thanks,

Bart.