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SubjectRe: [PATCH v2] netlink: do not proceed if dump's start() errs
On Thu, Sep 28, 2017 at 12:41:44AM +0200, Jason A. Donenfeld wrote:
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 327807731b44..94c11cf0459d 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2270,10 +2270,13 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
>
> mutex_unlock(nlk->cb_mutex);
>
> + ret = 0;
> if (cb->start)
> - cb->start(cb);
> + ret = cb->start(cb);
> +
> + if (!ret)
> + ret = netlink_dump(sk);
>
> - ret = netlink_dump(sk);
> sock_put(sk);
>
> if (ret)


FYI, using this horrific hack to currently work around bug:

#define KERNEL_VERSION_THAT_HAS_NETLINK_START_FIX KERNEL_VERSION(4, 14, 0) /* Hopefully! */

static int get(struct sk_buff *skb, struct netlink_callback *cb)
{
#if LINUX_VERSION_CODE < KERNEL_VERSION_THAT_HAS_NETLINK_START_FIX
/* https://marc.info/?l=linux-netdev&m=150655213004221&w=2 */
if (!cb->args[0]) {
ret = get_start(cb);
if (ret)
return ret;
}
#endif
...
}

static const struct genl_ops genl_ops[] = {
{
.cmd = CMD_GET,
#if LINUX_VERSION_CODE >= KERNEL_VERSION_THAT_HAS_NETLINK_START_FIX
/* https://marc.info/?l=linux-netdev&m=150655213004221&w=2 */
.start = get_start,
#endif
.dumpit = get,
...
}
}

Gross.

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