Subject: Re: [net RFC v1 1/1] page_pool: fix NULL dereference crash

From: Colin Foster <[email-masked]>
Date: Fri, 21 Jan 2022 18:40:51 -0800

On Fri, Jan 21, 2022 at 05:13:28PM -0800, Alexei Starovoitov wrote:
> On Fri, Jan 21, 2022 at 4:57 PM Colin Foster
> <[email-masked]> wrote:
> >
> > Check for the existence of page pool params before dereferencing. This can
> > cause crashes in certain conditions.
> 
> In what conditions?
> Out of tree driver?
> 
> > Fixes: 35b2e549894b ("page_pool: Add callback to init pages when they are
> > allocated")
> >
> > Signed-off-by: Colin Foster <[email-masked]>
> > ---
> >  net/core/page_pool.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> > index bd62c01a2ec3..641f849c95e7 100644
> > --- a/net/core/page_pool.c
> > +++ b/net/core/page_pool.c
> > @@ -213,7 +213,7 @@ static void page_pool_set_pp_info(struct page_pool *pool,
> >  {
> >         page->pp = pool;
> >         page->pp_magic |= PP_SIGNATURE;
> > -       if (pool->p.init_callback)
> > +       if (pool->p && pool->p.init_callback)

And my apologies - this should be if (pool... not if (pool->p. kernelbot
will be sure to tell me of this blunder soon

> >                 pool->p.init_callback(page, pool->p.init_arg);
> >  }
> >
> > --
> > 2.25.1
> >