Re: [PATCH v3] staging: rtl8723bs: os_dep: avoid NULL pointer dereference in rtw_cbuf_alloc

[Dan Carpenter <error27@gmail.com>]

On Tue, Apr 14, 2026 at 10:46:13AM +0300, Andy Shevchenko wrote:
> On Tue, Apr 14, 2026 at 12:43:06PM +0530, Shyam Sunder Reddy Padira wrote:
> > The return value of kzalloc_flex() is used without
> > ensuring that the allocation succeeded, and the
> > pointer is dereferenced unconditionally.
> > 
> > Guard the access to the allocated structure to
> > avoid a potential NULL pointer dereference if the
> > allocation fails.
> 
> You have a procedural issue here: please avoid sending a new patch version in
> the same email thread. It makes things harder to follow. For example, I usually
> mark the entire thread as read if I see some comments and don't want to go into
> the details. It effectively means that I will never see the new version that
> already was in the same thread!
> 
> ...
> 
> > --- a/drivers/staging/rtl8723bs/os_dep/osdep_service.c
> > +++ b/drivers/staging/rtl8723bs/os_dep/osdep_service.c
> > @@ -194,7 +194,8 @@ struct rtw_cbuf *rtw_cbuf_alloc(u32 size)
> >  	struct rtw_cbuf *cbuf;
> >  
> >  	cbuf = kzalloc_flex(*cbuf, bufs, size);
> > -	cbuf->size = size;
> > +	if (cbuf)
> > +		cbuf->size = size;
> >  
> >  	return cbuf;
> 
> Now to the code. This is still buggy. The problem is that the size is not
> validated and when it's 0, the same issue (dereference of invalid pointer)
> will happen.
> 
> Dan, JFYI k*alloc*(0) returns not NULL and not valid pointer.

kzalloc_flex() basically can't return the ZERO_SIZE pointer.  You
would need to pass an empty struct, which is really rare.  It can't
that here for sure.

regards,
dan carpenter