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From:   Justin Stitt <justinstitt@google.com>
Date:   Mon, 16 Oct 2023 13:52:21 -0700
Message-ID: <CAFhGd8rm=KJyinG-aqFj75JqQnC0=_+6NSbcdr=wG7SqXCsppQ@mail.gmail.com>
Subject: Re: [PATCH] brcmfmac: replace deprecated strncpy with strscpy
To:     Arend van Spriel <aspriel@gmail.com>,
        Franky Lin <franky.lin@broadcom.com>,
        Hante Meuleman <hante.meuleman@broadcom.com>,
        Kalle Valo <kvalo@kernel.org>
Cc:     linux-wireless@vger.kernel.org,
        brcm80211-dev-list.pdl@broadcom.com,
        SHA-cyfmac-dev-list@infineon.com, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
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On Mon, Oct 16, 2023 at 1:48=E2=80=AFPM Justin Stitt <justinstitt@google.co=
m> 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 ifp->ndev->name to be NUL-terminated based on its use in
> format strings within core.c:
> via brcmf_ifname() ->
> 67 |       char *brcmf_ifname(struct brcmf_if *ifp)
> 68 |       {
> 69 |            if (!ifp)
> 70 |                    return "<if_null>";
> 71 |
> 72 |            if (ifp->ndev)
> 73 |                    return ifp->ndev->name;
> 74 |
> 75 |            return "<if_none>";
> 76 |       }
> ...
> 288 |       static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *sk=
b,
> 289 |                                              struct net_device *nde=
v) {
> ...
> 330 |       brcmf_dbg(INFO, "%s: insufficient headroom (%d)\n",
> 331 |                 brcmf_ifname(ifp), head_delta);
> ...
> 336 |       bphy_err(drvr, "%s: failed to expand headroom\n",
> 337 |                brcmf_ifname(ifp));
>
> 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.
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strn=
cpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.h=
tml [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>
> ---
> Note: build-tested only.
>
> Found with: $ rg "strncpy\("
> ---
>  drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c =
b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index 2a90bb24ba77..7daa418df877 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> @@ -866,7 +866,7 @@ struct wireless_dev *brcmf_apsta_add_vif(struct wiphy=
 *wiphy, const char *name,
>                 goto fail;
>         }
>
> -       strncpy(ifp->ndev->name, name, sizeof(ifp->ndev->name) - 1);
> +       strscpy(ifp->ndev->name, name, sizeof(ifp->ndev->name));
>         err =3D brcmf_net_attach(ifp, true);
>         if (err) {
>                 bphy_err(drvr, "Registering netdevice failed\n");
>
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231016-strncpy-drivers-net-wireless-broadcom-brcm80211-brcmf=
mac-cfg80211-c-a20108421685
>
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
>

Ignore this patch. It will be rolled into a series with others.

Just found some more strncpy uses in broadcom/brcm80211 so I will make a se=
ries
fixing them all at once.


Thanks
Justin