linux-kernel - Re: [PATCH net] ptr_ring: fail early if queue occupies more than KMALLOC_MAX

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Message-ID: <20180207171422-mutt-send-email-mst@kernel.org>
Date:   Wed, 7 Feb 2018 17:15:35 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net] ptr_ring: fail early if queue occupies more than
 KMALLOC_MAX_SIZE

On Wed, Feb 07, 2018 at 05:17:59PM +0800, Jason Wang wrote:
> 
> 
> On 2018年02月07日 16:08, Jason Wang wrote:
> > To avoid slab to warn about exceeded size, fail early if queue
> > occupies more than KMALLOC_MAX_SIZE.
> > 
> > Reported-by: syzbot+e4d4f9ddd4295539735d@...kaller.appspotmail.com
> > Signed-off-by: Jason Wang <jasowang@...hat.com>
> > ---
> >   include/linux/ptr_ring.h | 2 ++
> >   1 file changed, 2 insertions(+)
> > 
> > diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> > index 1883d61..4b862da 100644
> > --- a/include/linux/ptr_ring.h
> > +++ b/include/linux/ptr_ring.h
> > @@ -466,6 +466,8 @@ static inline int ptr_ring_consume_batched_bh(struct ptr_ring *r,
> >   static inline void **__ptr_ring_init_queue_alloc(unsigned int size, gfp_t gfp)
> >   {
> > +	if (size > KMALLOC_MAX_SIZE)
> > +		return NULL;
> >   	return kcalloc(size, sizeof(void *), gfp);
> >   }
> 
> Fixes: 2e0ab8ca83c12 ("ptr_ring: array based FIFO for pointers")

That's probably not enough. How about switching to kvmalloc and limiting
this drastically to e.g. 64K. I vaguely remember that some wise man said
that should be enough for everybody :)

-- 
MST