2022-04-24 04:19:28

by Vihas Makwana

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

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 <[email protected]>
---
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

2022-04-24 08:28:16

by Fabio M. De Francesco

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

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 <[email protected]>
> ---
> 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
>

2022-04-24 09:47:02

by Vihas Makwana

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

On Sun, Apr 24, 2022 at 5:17 AM Fabio M. De Francesco
<[email protected]> 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 <[email protected]>
> > ---
> > 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

2022-04-25 11:38:25

by Dan Carpenter

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

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 <[email protected]>
> ---
> 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

2022-04-25 11:58:31

by Vihas Makwana

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

Please ignore this patch, Greg.