From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [PATCH] netfilter: fix possible ZERO_SIZE_PTR pointer dereferencing error. Date: Wed, 1 Jun 2016 11:27:11 +0200 Message-ID: <20160601092711.GB2711@salvia> References: <1464770068-7508-1-git-send-email-lixiubo@cmss.chinamobile.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kaber@trash.net, kadlec@blackhole.kfki.hu, davem@davemloft.net, netfilter-devel@vger.kernel.org, netfilter@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org To: Xiubo Li Return-path: Content-Disposition: inline In-Reply-To: <1464770068-7508-1-git-send-email-lixiubo@cmss.chinamobile.com> Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org On Wed, Jun 01, 2016 at 04:34:28PM +0800, Xiubo Li wrote: > Since we cannot make sure the 'hook_mask' will always be none zero > here. If it equals to zero, the num_hooks will be zero too, and then > kmalloc() will return ZERO_SIZE_PTR, which is (void *)16. > > Then the following error check will fails: > ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL); > if (ops == NULL) > return ERR_PTR(-ENOMEM); > > So this patch fix this with just doing the zero check before calling > kmalloc() is called. > > Maybe the case above will never happen here, but in theory. > > Signed-off-by: Xiubo Li > --- > net/netfilter/x_tables.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c > index c8a0b7d..4df8e38 100644 > --- a/net/netfilter/x_tables.c > +++ b/net/netfilter/x_tables.c > @@ -1185,6 +1185,9 @@ struct nf_hook_ops *xt_hook_link(const struct xt_table *table, nf_hookfn *fn) What kernel version are you using? I don't see xt_hook_link() in the development tree. > struct nf_hook_ops *ops; > int ret; > > + if (!num_hooks) > + return ERR_PTR(-EINVAL); > + > ops = kmalloc(sizeof(*ops) * num_hooks, GFP_KERNEL); > if (ops == NULL) > return ERR_PTR(-ENOMEM); > -- > 1.8.3.1 > > >