[PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[Kang Chen]

kzalloc may fails, pdata_attr might be null and will cause
illegal address access later.

Signed-off-by: Kang Chen <void0red@gmail.com>
---
 drivers/staging/r8188eu/core/rtw_p2p.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/r8188eu/core/rtw_p2p.c b/drivers/staging/r8188eu/core/rtw_p2p.c
index 93d3c9c43..802e1170a 100644
--- a/drivers/staging/r8188eu/core/rtw_p2p.c
+++ b/drivers/staging/r8188eu/core/rtw_p2p.c
@@ -31,6 +31,8 @@ static u32 go_add_group_info_attr(struct wifidirect_info *pwdinfo, u8 *pbuf)
 	struct sta_priv *pstapriv = &padapter->stapriv;
 
 	pdata_attr = kzalloc(MAX_P2P_IE_LEN, GFP_KERNEL);
+	if (!pdata_attr)
+		return 0;
 
 	pstart = pdata_attr;
 	pcur = pdata_attr;
-- 
2.34.1

Re: [PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[Dan Carpenter]

On Sun, Feb 26, 2023 at 09:25:00PM +0800, Kang Chen wrote:
> kzalloc may fails, pdata_attr might be null and will cause
> illegal address access later.
> 
> Signed-off-by: Kang Chen <void0red@gmail.com>
> ---
>  drivers/staging/r8188eu/core/rtw_p2p.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/staging/r8188eu/core/rtw_p2p.c b/drivers/staging/r8188eu/core/rtw_p2p.c
> index 93d3c9c43..802e1170a 100644
> --- a/drivers/staging/r8188eu/core/rtw_p2p.c
> +++ b/drivers/staging/r8188eu/core/rtw_p2p.c
> @@ -31,6 +31,8 @@ static u32 go_add_group_info_attr(struct wifidirect_info *pwdinfo, u8 *pbuf)
>  	struct sta_priv *pstapriv = &padapter->stapriv;
>  
>  	pdata_attr = kzalloc(MAX_P2P_IE_LEN, GFP_KERNEL);
> +	if (!pdata_attr)
> +		return 0;

Return success here is not a good thing.  We have to fix the caller to
check for errors.  (Fixing a bug half way just makes it harder to find
the bug so it makes the situation worse).

regards,
dan carpenter

Re: [PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[Kang Chen]

Hi, Dan,

Thanks for your review.
I noticed there is no error handling in the origin design (this call chain).
go_add_group_info_attr returns a len-like value indicating the length
of pbuf.
I don't think throwing an error to the caller is a good idea, the caller
doesn't seem to care about it.
So inserting a netdev_dbg or pr_debug here might be enough.
Do you have a better idea?

Best regards,
Kang Chen


On Mon, Feb 27, 2023 at 12:47 PM Dan Carpenter <error27@gmail.com> wrote:
>
> On Sun, Feb 26, 2023 at 09:25:00PM +0800, Kang Chen wrote:
> > kzalloc may fails, pdata_attr might be null and will cause
> > illegal address access later.
> >
> > Signed-off-by: Kang Chen <void0red@gmail.com>
> > ---
> >  drivers/staging/r8188eu/core/rtw_p2p.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/staging/r8188eu/core/rtw_p2p.c b/drivers/staging/r8188eu/core/rtw_p2p.c
> > index 93d3c9c43..802e1170a 100644
> > --- a/drivers/staging/r8188eu/core/rtw_p2p.c
> > +++ b/drivers/staging/r8188eu/core/rtw_p2p.c
> > @@ -31,6 +31,8 @@ static u32 go_add_group_info_attr(struct wifidirect_info *pwdinfo, u8 *pbuf)
> >       struct sta_priv *pstapriv = &padapter->stapriv;
> >
> >       pdata_attr = kzalloc(MAX_P2P_IE_LEN, GFP_KERNEL);
> > +     if (!pdata_attr)
> > +             return 0;
>
> Return success here is not a good thing.  We have to fix the caller to
> check for errors.  (Fixing a bug half way just makes it harder to find
> the bug so it makes the situation worse).
>
> regards,
> dan carpenter
>

Re: [PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[Dan Carpenter]

On Mon, Feb 27, 2023 at 03:11:21PM +0800, Kang Chen wrote:
> Hi, Dan,
> 
> Thanks for your review.
> I noticed there is no error handling in the origin design (this call chain).
> go_add_group_info_attr returns a len-like value indicating the length
> of pbuf.
> I don't think throwing an error to the caller is a good idea, the caller
> doesn't seem to care about it.
> So inserting a netdev_dbg or pr_debug here might be enough.
> Do you have a better idea?

As I mentioned in my email, we need to fix the caller to care about it.

regards,
dan carpenter

> 
> Best regards,
> Kang Chen
> 
> 
> On Mon, Feb 27, 2023 at 12:47 PM Dan Carpenter <error27@gmail.com> wrote:
> >
> > On Sun, Feb 26, 2023 at 09:25:00PM +0800, Kang Chen wrote:
> > > kzalloc may fails, pdata_attr might be null and will cause
> > > illegal address access later.
> > >
> > > Signed-off-by: Kang Chen <void0red@gmail.com>
> > > ---
> > >  drivers/staging/r8188eu/core/rtw_p2p.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/staging/r8188eu/core/rtw_p2p.c b/drivers/staging/r8188eu/core/rtw_p2p.c
> > > index 93d3c9c43..802e1170a 100644
> > > --- a/drivers/staging/r8188eu/core/rtw_p2p.c
> > > +++ b/drivers/staging/r8188eu/core/rtw_p2p.c
> > > @@ -31,6 +31,8 @@ static u32 go_add_group_info_attr(struct wifidirect_info *pwdinfo, u8 *pbuf)
> > >       struct sta_priv *pstapriv = &padapter->stapriv;
> > >
> > >       pdata_attr = kzalloc(MAX_P2P_IE_LEN, GFP_KERNEL);
> > > +     if (!pdata_attr)
> > > +             return 0;
> >
> > Return success here is not a good thing.  We have to fix the caller to
> > check for errors.  (Fixing a bug half way just makes it harder to find
> > the bug so it makes the situation worse).
> >
> > regards,
> > dan carpenter
> >

Re: [PATCH] staging: r8188eu: add a null check of kzalloc in go_add_group_info_attr

[Dan Carpenter]

On Mon, Feb 27, 2023 at 03:11:21PM +0800, Kang Chen wrote:
> Hi, Dan,
> 
> Thanks for your review.
> I noticed there is no error handling in the origin design (this call chain).
> go_add_group_info_attr returns a len-like value indicating the length
> of pbuf.
> I don't think throwing an error to the caller is a good idea, the caller
> doesn't seem to care about it.
> So inserting a netdev_dbg or pr_debug here might be enough.
> Do you have a better idea?
> 

The bug is real, yes.  But you have your static checker which can detect
it and I also have an unpublished static checker test which detects this
bug.

drivers/staging/r8188eu/core/rtw_p2p.c:106 go_add_group_info_attr() warn: 'pdata_attr' was never checked for NULL

If we just hide the bug enough for so that the static checker cannot
find the bug then we're taking a step backward.  When this driver is
ready to leave staging then normally I review every static checker
warning.  But if we hide the warning then it will never be fixed.

regards,
dan carpenter