From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jakub Kicinski Subject: Re: [PATCH V2 bpf] xdp: add NULL pointer check in __xdp_return() Date: Wed, 25 Jul 2018 19:11:49 -0700 Message-ID: <20180725191149.34242252@cakuba.netronome.com> References: <20180725150950.23298-1-ap420073@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: daniel@iogearbox.net, ast@kernel.org, bjorn.topel@intel.com, brouer@redhat.com, netdev@vger.kernel.org To: Taehee Yoo Return-path: Received: from mail-qk0-f195.google.com ([209.85.220.195]:36037 "EHLO mail-qk0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728507AbeGZD0W (ORCPT ); Wed, 25 Jul 2018 23:26:22 -0400 Received: by mail-qk0-f195.google.com with SMTP id a132-v6so96087qkg.3 for ; Wed, 25 Jul 2018 19:11:54 -0700 (PDT) In-Reply-To: <20180725150950.23298-1-ap420073@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 26 Jul 2018 00:09:50 +0900, Taehee Yoo wrote: > rhashtable_lookup() can return NULL. so that NULL pointer > check routine should be added. > > Fixes: 02b55e5657c3 ("xdp: add MEM_TYPE_ZERO_COPY") > Signed-off-by: Taehee Yoo > --- > V2 : add WARN_ON_ONCE when xa is NULL. > > net/core/xdp.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/net/core/xdp.c b/net/core/xdp.c > index 9d1f220..786fdbe 100644 > --- a/net/core/xdp.c > +++ b/net/core/xdp.c > @@ -345,7 +345,10 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct, > rcu_read_lock(); > /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */ > xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params); > - xa->zc_alloc->free(xa->zc_alloc, handle); > + if (!xa) > + WARN_ON_ONCE(1); nit: is compiler smart enough to figure out the fast path here? WARN_ON_ONCE() has the nice side effect of wrapping the condition in unlikely(). It could save us both LoC and potentially cycles to do: if (!WARN_ON_ONCE(!xa)) xa->zc_alloc->free(xa->zc_alloc, handle); Although it admittedly looks a bit awkward. I'm not sure if we have some form of assert (i.e. positive check) in tree :S > + else > + xa->zc_alloc->free(xa->zc_alloc, handle); > rcu_read_unlock(); > default: > /* Not possible, checked in xdp_rxq_info_reg_mem_model() */