linux-kernel - RE: [PATCH] staging/rtl8192u: Remove all strcpy() uses in favor of strscpy()

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Date:   Mon, 19 Jul 2021 08:49:54 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Len Baker' <len.baker@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Lee Jones <lee.jones@...aro.org>,
        Romain Perier <romain.perier@...il.com>,
        Allen Pais <apais@...ux.microsoft.com>,
        Dmitrii Wolf <dev.dragon@...ru>,
        "Iain Craig" <coldcity@...il.com>,
        "linux-staging@...ts.linux.dev" <linux-staging@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] staging/rtl8192u: Remove all strcpy() uses in favor of
 strscpy()

From: Len Baker
> Sent: 18 July 2021 12:32
> 
> strcpy() performs no bounds checking on the destination buffer. This
> could result in linear overflows beyond the end of the buffer, leading
> to all kinds of misbehaviors. The safe replacement is strscpy().
> 
> Signed-off-by: Len Baker <len.baker@....com>
> ---
>  drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
> b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
> index ab885353f668..1a193f900779 100644
> --- a/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
> +++ b/drivers/staging/rtl8192u/ieee80211/ieee80211_softmac.c
> @@ -2226,7 +2226,8 @@ static void ieee80211_start_ibss_wq(struct work_struct *work)
>  	mutex_lock(&ieee->wx_mutex);
> 
>  	if (ieee->current_network.ssid_len == 0) {
> -		strcpy(ieee->current_network.ssid, IEEE80211_DEFAULT_TX_ESSID);
> +		strscpy(ieee->current_network.ssid, IEEE80211_DEFAULT_TX_ESSID,
> +			sizeof(ieee->current_network.ssid));

I'm pretty sure that recent compiler releases know enough
about strcpy() to error overflows for strcpy() from quoted
strings into char[].

If these checks are enabled for kernel builds then they are
actually safer than the run-time check above
(which can be mistyped).

The compiler can (it may not) convert the strcpy() into a memcpy()
using the compile-time length of the quoted string.

	David

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