linux-kernel - Re: [PATCH net] net: bridge: fix uninitialized variables when BRIDGE

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Message-ID: <20211027161440.00cb1107@ceranb>
Date:   Wed, 27 Oct 2021 16:14:40 +0200
From:   Ivan Vecera <ivecera@...hat.com>
To:     Nikolay Aleksandrov <nikolay@...dia.com>
Cc:     netdev@...r.kernel.org, Roopa Prabhu <roopa@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Henrik Bjoernlund <henrik.bjoernlund@...rochip.com>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: bridge: fix uninitialized variables when
 BRIDGE_CFM is disabled

On Wed, 27 Oct 2021 16:54:39 +0300
Nikolay Aleksandrov <nikolay@...dia.com> wrote:

> On 27/10/2021 16:49, Ivan Vecera wrote:
> > Function br_get_link_af_size_filtered() calls br_cfm_{,peer}_mep_count()
> > but does not check their return value. When BRIDGE_CFM is not enabled
> > these functions return -EOPNOTSUPP but do not modify count parameter.
> > Calling function then works with uninitialized variables.
> > 
> > Fixes: b6d0425b816e ("bridge: cfm: Netlink Notifications.")
> > Signed-off-by: Ivan Vecera <ivecera@...hat.com>
> > ---
> >  net/bridge/br_netlink.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
> > index 5c6c4305ed23..12d602495ea0 100644
> > --- a/net/bridge/br_netlink.c
> > +++ b/net/bridge/br_netlink.c
> > @@ -126,8 +126,10 @@ static size_t br_get_link_af_size_filtered(const struct net_device *dev,
> >  		return vinfo_sz;
> >  
> >  	/* CFM status info must be added */
> > -	br_cfm_mep_count(br, &num_cfm_mep_infos);
> > -	br_cfm_peer_mep_count(br, &num_cfm_peer_mep_infos);
> > +	if (br_cfm_mep_count(br, &num_cfm_mep_infos) < 0)
> > +		num_cfm_mep_infos = 0;
> > +	if (br_cfm_peer_mep_count(br, &num_cfm_peer_mep_infos) < 0)
> > +		num_cfm_peer_mep_infos = 0;
> >  
> >  	vinfo_sz += nla_total_size(0);	/* IFLA_BRIDGE_CFM */
> >  	/* For each status struct the MEP instance (u32) is added */
> >   
> 
> Hi,
> Could you please rather update the EOPNOTSUPP helpers to set these infos to 0 before
> returning? Someone else might decide to use them and hit the same bug.
> 
> E.g.
> static inline int br_cfm_mep_count(struct net_bridge *br, u32 *count)
> {
> 	*count = 0;
>         return -EOPNOTSUPP;
> }
> 
> We already do the same for br_allowed_ingress, nbp_vlan_add() etc.
> 
> Thanks,
>  Nik
> 

Ok, Nik... works for me.

Thanks,
Ivan