netdev - Re: [PATCH] rndis_wlan: Prevent buffer overflow in rndis_query

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Message-ID: <5ab09d55233d1ba5969bd6a02214046c24145527.camel@suse.de>
Date:   Fri, 13 Jan 2023 09:42:40 +0100
From:   cahu <cahu@...e.de>
To:     Szymon Heidrich <szymon.heidrich@...il.com>, kvalo@...nel.org,
        jussi.kivilinna@....fi, davem@...emloft.net
Cc:     edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rndis_wlan: Prevent buffer overflow in rndis_query_oid

Mitre assigned CVE-2023-23559 for this.

On Tue, 2023-01-10 at 18:30 +0100, Szymon Heidrich wrote:
> Since resplen and respoffs are signed integers sufficiently
> large values of unsigned int len and offset members of RNDIS
> response will result in negative values of prior variables.
> This may be utilized to bypass implemented security checks
> to either extract memory contents by manipulating offset or
> overflow the data buffer via memcpy by manipulating both
> offset and len.
> 
> Additionally assure that sum of resplen and respoffs does not
> overflow so buffer boundaries are kept.
> 
> Fixes: 80f8c5b434f9 ("rndis_wlan: copy only useful data from
> rndis_command respond")
> Signed-off-by: Szymon Heidrich <szymon.heidrich@...il.com>
> ---
>  drivers/net/wireless/rndis_wlan.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/rndis_wlan.c
> b/drivers/net/wireless/rndis_wlan.c
> index 82a7458e0..d7fc05328 100644
> --- a/drivers/net/wireless/rndis_wlan.c
> +++ b/drivers/net/wireless/rndis_wlan.c
> @@ -697,7 +697,7 @@ static int rndis_query_oid(struct usbnet *dev,
> u32 oid, void *data, int *len)
>                 struct rndis_query_c    *get_c;
>         } u;
>         int ret, buflen;
> -       int resplen, respoffs, copylen;
> +       u32 resplen, respoffs, copylen;
>  
>         buflen = *len + sizeof(*u.get);
>         if (buflen < CONTROL_BUFFER_SIZE)
> @@ -740,7 +740,7 @@ static int rndis_query_oid(struct usbnet *dev,
> u32 oid, void *data, int *len)
>                         goto exit_unlock;
>                 }
>  
> -               if ((resplen + respoffs) > buflen) {
> +               if (resplen > (buflen - respoffs)) {
>                         /* Device would have returned more data if
> buffer would
>                          * have been big enough. Copy just the bits
> that we got.
>                          */


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