netdev - Re: [PATCH net] net: bridge: vlan: Fix dumping with ifindex

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Message-ID: <YfC37T23elbsAD0R@d3>
Date:   Wed, 26 Jan 2022 11:54:37 +0900
From:   Benjamin Poirier <bpoirier@...dia.com>
To:     Nikolay Aleksandrov <nikolay@...dia.com>
CC:     Roopa Prabhu <roopa@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        <bridge@...ts.linux-foundation.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net] net: bridge: vlan: Fix dumping with ifindex

On 2022-01-25 11:51 +0200, Nikolay Aleksandrov wrote:
> On 25/01/2022 10:24, Nikolay Aleksandrov wrote:
> > On 25/01/2022 08:19, Benjamin Poirier wrote:
> >> Specifying ifindex in a RTM_GETVLAN dump leads to an infinite repetition
> >> of the same entries. netlink_dump() normally calls the dump function
> >> repeatedly until it returns 0 which br_vlan_rtm_dump() never does in
> >> that case.
> >>
> >> Fixes: 8dcea187088b ("net: bridge: vlan: add rtm definitions and dump support")
> >> Signed-off-by: Benjamin Poirier <bpoirier@...dia.com>
> >> ---
> >>  net/bridge/br_vlan.c | 6 ++++--
> >>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> > [snip]
> >>
> >> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> >> index 84ba456a78cc..2e606f2b9a4d 100644
> >> --- a/net/bridge/br_vlan.c
> >> +++ b/net/bridge/br_vlan.c
> >> @@ -2013,7 +2013,7 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
> >>  		dump_flags = nla_get_u32(dtb[BRIDGE_VLANDB_DUMP_FLAGS]);
> >>  
> >>  	rcu_read_lock();
> >> -	if (bvm->ifindex) {
> >> +	if (bvm->ifindex && !s_idx) {
> >>  		dev = dev_get_by_index_rcu(net, bvm->ifindex);
> >>  		if (!dev) {
> >>  			err = -ENODEV;
> >> @@ -2022,7 +2022,9 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
> >>  		err = br_vlan_dump_dev(dev, skb, cb, dump_flags);
> >>  		if (err && err != -EMSGSIZE)
> >>  			goto out_err;
> >> -	} else {
> >> +		else if (!err)
> >> +			idx++;
> >> +	} else if (!bvm->ifindex) {
> >>  		for_each_netdev_rcu(net, dev) {
> >>  			if (idx < s_idx)
> >>  				goto skip;
> > 
> > Acked-by: Nikolay Aleksandrov <nikolay@...dia.com>
> 
> Actually I'd prefer an alternative that would encapsulate handling the single
> device dump in its block, avoid all the "else if"s and is simpler (untested):
> 
> diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
> index 84ba456a78cc..43201260e37b 100644
> --- a/net/bridge/br_vlan.c
> +++ b/net/bridge/br_vlan.c
> @@ -2020,7 +2020,8 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
>                         goto out_err;
>                 }
>                 err = br_vlan_dump_dev(dev, skb, cb, dump_flags);
> -               if (err && err != -EMSGSIZE)
> +               /* if the dump completed without an error we return 0 here */
> +               if (err != -EMSGSIZE)
>                         goto out_err;
>         } else {
>                 for_each_netdev_rcu(net, dev) {

LGTM, thank you.