linux-hardening - Re: [PATCH] qlcnic: replace deprecated strncpy with strscpy

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Date: Mon, 16 Oct 2023 11:14:29 -0700
From: Justin Stitt <justinstitt@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: Shahed Shaikh <shshaikh@...vell.com>, Manish Chopra <manishc@...vell.com>, 
	GR-Linux-NIC-Dev@...vell.com, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] qlcnic: replace deprecated strncpy with strscpy

On Sat, Oct 14, 2023 at 7:47 PM Kees Cook <keescook@...omium.org> wrote:
>
> On Thu, Oct 12, 2023 at 07:44:29PM +0000, Justin Stitt wrote:
> > strncpy() is deprecated for use on NUL-terminated destination strings
> > [1] and as such we should prefer more robust and less ambiguous string
> > interfaces.
> >
> > We expect fw_info->fw_file_name to be NUL-terminated based on its use
> > within _request_firmware_prepare() wherein `name` refers to it:
> > |       if (firmware_request_builtin_buf(firmware, name, dbuf, size)) {
> > |               dev_dbg(device, "using built-in %s\n", name);
> > |               return 0; /* assigned */
> > |       }
> > ... and with firmware_request_builtin() also via `name`:
> > |       if (strcmp(name, b_fw->name) == 0) {
> >
> > There is no evidence that NUL-padding is required.
> >
> > Considering the above, a suitable replacement is `strscpy` [2] due to
> > the fact that it guarantees NUL-termination on the destination buffer
> > without unnecessarily NUL-padding.
>
> When doing the hard-coded value to sizeof(), can you include in the
> commit log the rationale for it? For example:
>
>   Additionally replace size macro (QLC_FW_FILE_NAME_LEN) with
>   sizeof(fw_info->fw_file_name) to more directly tie the maximum buffer
>   size to the destination buffer:
>
>   struct qlc_83xx_fw_info {
>           ...
>           char    fw_file_name[QLC_FW_FILE_NAME_LEN];
>   };
>

Sure, I'll be doing this from now on to make the change more clear!

>
> >
> > Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> > Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@...r.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> > ---
> > Note: build-tested only.
> >
> > Found with: $ rg "strncpy\("
> > ---
> >  drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> > index c95d56e56c59..b733374b4dc5 100644
> > --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> > +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_init.c
> > @@ -2092,8 +2092,8 @@ static int qlcnic_83xx_run_post(struct qlcnic_adapter *adapter)
> >               return -EINVAL;
> >       }
> >
> > -     strncpy(fw_info->fw_file_name, QLC_83XX_POST_FW_FILE_NAME,
> > -             QLC_FW_FILE_NAME_LEN);
> > +     strscpy(fw_info->fw_file_name, QLC_83XX_POST_FW_FILE_NAME,
> > +             sizeof(fw_info->fw_file_name));
> >
> >       ret = request_firmware(&fw_info->fw, fw_info->fw_file_name, dev);
> >       if (ret) {
> > @@ -2396,12 +2396,12 @@ static int qlcnic_83xx_get_fw_info(struct qlcnic_adapter *adapter)
> >               switch (pdev->device) {
> >               case PCI_DEVICE_ID_QLOGIC_QLE834X:
> >               case PCI_DEVICE_ID_QLOGIC_QLE8830:
> > -                     strncpy(fw_info->fw_file_name, QLC_83XX_FW_FILE_NAME,
> > -                             QLC_FW_FILE_NAME_LEN);
> > +                     strscpy(fw_info->fw_file_name, QLC_83XX_FW_FILE_NAME,
> > +                             sizeof(fw_info->fw_file_name));
> >                       break;
> >               case PCI_DEVICE_ID_QLOGIC_QLE844X:
> > -                     strncpy(fw_info->fw_file_name, QLC_84XX_FW_FILE_NAME,
> > -                             QLC_FW_FILE_NAME_LEN);
> > +                     strscpy(fw_info->fw_file_name, QLC_84XX_FW_FILE_NAME,
> > +                             sizeof(fw_info->fw_file_name));
> >                       break;
> >               default:
> >                       dev_err(&pdev->dev, "%s: Invalid device id\n",
>
> But yes, this all looks right to me.
>
> Reviewed-by: Kees Cook <keescook@...omium.org>
>
> --
> Kees Cook

Thanks
Justin