Re: [PATCH v2] vfio: Clear the caps->buf to NULL after free

[Schspa Shi]

Cornelia Huck <cohuck@xxxxxxxxxx> writes:

> On Tue, Jun 28 2022, Alex Williamson 
> <alex.williamson@xxxxxxxxxx> wrote:
>
> > On Tue, 28 Jun 2022 23:24:29 +0800
> > Schspa Shi <schspa@xxxxxxxxx> wrote:
> >
> > > API vfio_info_cap_add will free caps->buf, clear it to NULL 
> > > after
> > > free.
> >
> > Should this be something like:
> >
> >     On buffer resize failure, vfio_info_cap_add() will free the 
> >     buffer,
> >     report zero for the size, and return -ENOMEM.  As 
> >     additional
> >     hardening, also clear the buffer pointer to prevent any 
> >     chance of a
> >     double free.
>
> I like that better. With that,
>
> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>

I have send a V3 patch for this comment change, please review it.

> > Thanks,
> > Alex
> >  
> > > Signed-off-by: Schspa Shi <schspa@xxxxxxxxx>
> > > ---
> > >  drivers/vfio/vfio.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> > > index 61e71c1154be..a0fb93866f61 100644
> > > --- a/drivers/vfio/vfio.c
> > > +++ b/drivers/vfio/vfio.c
> > > @@ -1812,6 +1812,7 @@ struct vfio_info_cap_header 
> > > *vfio_info_cap_add(struct vfio_info_cap *caps,
> > >  	buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
> > >  	if (!buf) {
> > >  		kfree(caps->buf);
> > > +		caps->buf = NULL;
> > >  		caps->size = 0;
> > >  		return ERR_PTR(-ENOMEM);
> > >  	}

--
BRs
Schspa Shi