[PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[Vihas Makwana]

recvframe_chk_defrag() performs a NULL check on psta, but if that check
fails then it dereferences it, which it shouldn't do as psta is NULL.

Set pdefrag_q to NULL if above check fails and let the code after it handle
that case.

Fixes: 1cc18a22b96b ("staging: r8188eu: Add files for new driver - part 5")
Signed-off-by: Vihas Makwana <makvihas@gmail.com>
---
 drivers/staging/r8188eu/core/rtw_recv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c
index c1005ddaa..db54bceff 100644
--- a/drivers/staging/r8188eu/core/rtw_recv.c
+++ b/drivers/staging/r8188eu/core/rtw_recv.c
@@ -1244,7 +1244,7 @@ struct recv_frame *recvframe_chk_defrag(struct adapter *padapter, struct recv_fr
 			pdefrag_q = NULL;
 		}
 	} else {
-		pdefrag_q = &psta->sta_recvpriv.defrag_q;
+		pdefrag_q = NULL;
 	}
 
 	if ((ismfrag == 0) && (fragnum == 0))
-- 
2.30.2

Re: [PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[Fabio M. De Francesco]

On sabato 23 aprile 2022 20:47:48 CEST Vihas Makwana wrote:
> recvframe_chk_defrag() performs a NULL check on psta, but if that check
> fails then it dereferences it, which it shouldn't do as psta is NULL.
> 
> Set pdefrag_q to NULL if above check fails and let the code after it 
handle
> that case.
> 
> Fixes: 1cc18a22b96b ("staging: r8188eu: Add files for new driver - part 
5")
> Signed-off-by: Vihas Makwana <makvihas@gmail.com>
> ---
>  drivers/staging/r8188eu/core/rtw_recv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/
r8188eu/core/rtw_recv.c
> index c1005ddaa..db54bceff 100644
> --- a/drivers/staging/r8188eu/core/rtw_recv.c
> +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> @@ -1244,7 +1244,7 @@ struct recv_frame *recvframe_chk_defrag(struct 
adapter *padapter, struct recv_fr
>  			pdefrag_q = NULL;
>  		}
>  	} else {
> -		pdefrag_q = &psta->sta_recvpriv.defrag_q;
> +		pdefrag_q = NULL;

Hi Vihas,

To me the code looks like this...

	struct sta_info *psta;
	...
	psta = rtw_get_stainfo(pstapriv, psta_addr);
	/* The code is about to test if "psta" is a valid pointer */
	if (!psta) {
		/* "psta" is NULL */		
		...
	} else {
		/* "psta" is not NULL */
		...

>  	}
>  

Also, even if "psta" were NULL (but it isn't), your change would still be 
no good.

Please be very careful with these types of changes next time :)

Thanks,

Fabio M. De Francesco

>  	if ((ismfrag == 0) && (fragnum == 0))
> -- 
> 2.30.2
>  

Re: [PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[Vihas Makwana]

On Sun, Apr 24, 2022 at 5:17 AM Fabio M. De Francesco
<fmdefrancesco@gmail.com> wrote:
>
> On sabato 23 aprile 2022 20:47:48 CEST Vihas Makwana wrote:
> > recvframe_chk_defrag() performs a NULL check on psta, but if that check
> > fails then it dereferences it, which it shouldn't do as psta is NULL.
> >
> > Set pdefrag_q to NULL if above check fails and let the code after it
> handle
> > that case.
> >
> > Fixes: 1cc18a22b96b ("staging: r8188eu: Add files for new driver - part
> 5")
> > Signed-off-by: Vihas Makwana <makvihas@gmail.com>
> > ---
> >  drivers/staging/r8188eu/core/rtw_recv.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/
> r8188eu/core/rtw_recv.c
> > index c1005ddaa..db54bceff 100644
> > --- a/drivers/staging/r8188eu/core/rtw_recv.c
> > +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> > @@ -1244,7 +1244,7 @@ struct recv_frame *recvframe_chk_defrag(struct
> adapter *padapter, struct recv_fr
> >                       pdefrag_q = NULL;
> >               }
> >       } else {
> > -             pdefrag_q = &psta->sta_recvpriv.defrag_q;
> > +             pdefrag_q = NULL;
>
> Hi Vihas,
>
> To me the code looks like this...
>
>         struct sta_info *psta;
>         ...
>         psta = rtw_get_stainfo(pstapriv, psta_addr);
>         /* The code is about to test if "psta" is a valid pointer */
>         if (!psta) {
>                 /* "psta" is NULL */
>                 ...
>         } else {
>                 /* "psta" is not NULL */
>                 ...
>
> >       }
> >
>
> Also, even if "psta" were NULL (but it isn't), your change would still be
> no good.
>
> Please be very careful with these types of changes next time :)
>
> Thanks,
>
> Fabio M. De Francesco
>
> >       if ((ismfrag == 0) && (fragnum == 0))
> > --
Oh yea, sorry about this. I don't know how I missed this.
Thanks for clarification Fabio. Will take care next time.


-- 
Thanks,
Vihas

Re: [PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[Vihas Makwana]

Please ignore this patch, Greg.

Re: [PATCH] staging: r8188eu: fix a potential NULL pointer dereference

[Dan Carpenter]

On Sun, Apr 24, 2022 at 12:17:48AM +0530, Vihas Makwana wrote:
> recvframe_chk_defrag() performs a NULL check on psta, but if that check
> fails then it dereferences it, which it shouldn't do as psta is NULL.
> 
> Set pdefrag_q to NULL if above check fails and let the code after it handle
> that case.
> 
> Fixes: 1cc18a22b96b ("staging: r8188eu: Add files for new driver - part 5")
> Signed-off-by: Vihas Makwana <makvihas@gmail.com>
> ---
>  drivers/staging/r8188eu/core/rtw_recv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c
> index c1005ddaa..db54bceff 100644
> --- a/drivers/staging/r8188eu/core/rtw_recv.c
> +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> @@ -1244,7 +1244,7 @@ struct recv_frame *recvframe_chk_defrag(struct adapter *padapter, struct recv_fr
>  			pdefrag_q = NULL;
>  		}
>  	} else {
> -		pdefrag_q = &psta->sta_recvpriv.defrag_q;
> +		pdefrag_q = NULL;

What?  "psta" is valid pointer on the else path.

(Also this isn't really a dereference, this is just pointer math.  It's
taking the address.  The Oops would happen later if psta were NULL.)

regards,
dan carpenter