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Re: [PATCHv3 2/2] IPVS: Add genetlink interface implementation

To: Sven Wegener <sven.wegener@xxxxxxxxxxx>
Subject: Re: [PATCHv3 2/2] IPVS: Add genetlink interface implementation
Cc: netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, horms@xxxxxxxxxxxx, kaber@xxxxxxxxx, davem@xxxxxxxxxxxxx, tgraf@xxxxxxx, vbusam@xxxxxxxxxx
From: juliusv@xxxxxxxxxx (Julius Volz)
Date: Thu, 14 Aug 2008 12:27:19 +0200
On Thu, Aug 14, 2008 at 12:04:50PM +0200, Sven Wegener wrote:
> On Thu, 14 Aug 2008, Julius Volz wrote:
> 
> > On Wed, Aug 13, 2008 at 11:51:06PM +0200, Sven Wegener wrote:
> > > On Fri, 8 Aug 2008, Julius Volz wrote:
> > > > +static int ip_vs_genl_get_cmd(struct sk_buff *skb, struct genl_info 
> > > > *info)
> > > > +{
> > > > +       struct sk_buff *msg;
> > > > +       void *reply;
> > > > +       int ret, cmd, reply_cmd;
> > > > +
> > > > +       mutex_lock(&__ip_vs_mutex);
> > > > +
> > > > +       cmd = info->genlhdr->cmd;
> > > > +
> > > > +       msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
> > > > +       if (!msg) {
> > > > +               ret = -ENOMEM;
> > > > +               goto out_err;
> > > 
> > > Here you want out...
> > > 
> > > > +       }
> > > > +
> > > > +       if (cmd == IPVS_CMD_GET_SERVICE)
> > > > +               reply_cmd = IPVS_CMD_NEW_SERVICE;
> > > > +       else if (cmd == IPVS_CMD_GET_INFO)
> > > > +               reply_cmd = IPVS_CMD_SET_INFO;
> > > > +       else if (cmd == IPVS_CMD_GET_CONFIG)
> > > > +               reply_cmd = IPVS_CMD_SET_CONFIG;
> > > > +       else {
> > > > +               IP_VS_ERR("unknown Generic Netlink command\n");
> > > > +               ret = -EINVAL;
> > > > +               goto out;
> > > 
> > > ..and here you want out_error, to not leak msg.
> > 
> > Ouch, thanks! Fixed this and locked the mutex later. I also removed the
> > "if (msg)" from out_err, as it becomes unneeded now. Here's the updated
> > patch:
> 
> You missed the static on the register and unregister functions down at the 
> bottom. :) Also see my comments to your change regarding the above issue 
> down here.

Hrm, yes!

> > +static int ip_vs_genl_get_cmd(struct sk_buff *skb, struct genl_info *info)
> > +{
> > +   struct sk_buff *msg;
> > +   void *reply;
> > +   int ret, cmd, reply_cmd;
> > +
> > +   cmd = info->genlhdr->cmd;
> > +
> > +   if (cmd == IPVS_CMD_GET_SERVICE)
> > +           reply_cmd = IPVS_CMD_NEW_SERVICE;
> > +   else if (cmd == IPVS_CMD_GET_INFO)
> > +           reply_cmd = IPVS_CMD_SET_INFO;
> > +   else if (cmd == IPVS_CMD_GET_CONFIG)
> > +           reply_cmd = IPVS_CMD_SET_CONFIG;
> > +   else {
> > +           IP_VS_ERR("unknown Generic Netlink command\n");
> > +           ret = -EINVAL;
> > +           goto out;
> > +   }
> > +
> > +   msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
> > +   if (!msg) {
> > +           ret = -ENOMEM;
> > +           goto out;
> > +   }
> > +
> > +   reply = genlmsg_put_reply(msg, info, &ip_vs_genl_family, 0, reply_cmd);
> > +   if (reply == NULL)
> > +           goto nla_put_failure;
> 
> These gotos now unlock a not locked mutex down in the error path.

What did they put into my water supply :-/ Thanks!

> 
> > +
> > +   mutex_lock(&__ip_vs_mutex);
> 
> Is there a reason not using mutex_lock_interruptible() like the sockopt 
> interface does? I wondered in your earlier patch, but didn't really 
> bother.

Not an expert here. I saw mutex_lock_interruptible() being used in the
old sockopt interface, but returning -ERESTARTSYS on interruption. Can I
do something similar to this from a genetlink function or what is the
right way? I was unsure, so I stuck to mutex_lock()...

Julius
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