linux-kernel - Re: [PATCH] scsi: qedf: replace memset/memcpy with safer strscpy

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Date:   Fri, 12 Apr 2019 11:36:27 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Colin King <colin.king@...onical.com>,
        QLogic-Storage-Upstream@...ium.com,
        "James E . J . Bottomley" <jejb@...ux.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scsi: qedf: replace memset/memcpy with safer strscpy

On 12/04/2019 11.05, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the qedf_dbg_* family of functions can overrun the end
> of the source string if it is less than the destination buffer
> length because of the use of a fixed sized memcpy. Replace the
> memset/memcpy calls with the safer strscpy as this won't overrun
> the end of the source string and it ensures the destination
> string is always terminated with NUL.
> 
> Addresses-Coverity: ("Out-of-bounds access")
> Fixes: 61d8658b4a43 ("scsi: qedf: Add QLogic FastLinQ offload FCoE driver framework.")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/scsi/qedf/qedf_dbg.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/qedf/qedf_dbg.c b/drivers/scsi/qedf/qedf_dbg.c
> index f2397ee9ba69..b491bebeaca9 100644
> --- a/drivers/scsi/qedf/qedf_dbg.c
> +++ b/drivers/scsi/qedf/qedf_dbg.c
> @@ -17,8 +17,7 @@ qedf_dbg_err(struct qedf_dbg_ctx *qedf, const char *func, u32 line,
>  	struct va_format vaf;
>  	char nfunc[32];
>  
> -	memset(nfunc, 0, sizeof(nfunc));
> -	memcpy(nfunc, func, sizeof(nfunc) - 1);
> +	strscpy(nfunc, func, sizeof(nfunc));

Why not drop the pointless nfunc and stack copying and just pass func as
the %s parameter; these are only called via macros that pass __func__ as
the func argument, and that is always a proper nul-terminated string.

Rasmus