From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
Subject: Re: [PATCH 02/10] userns: Add per user namespace sysctls.
Date: Wed, 20 Jul 2016 10:55:55 -0500
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To: "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org>
Cc: Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, Linux Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, Nikolay Borisov <kernel-6AxghH7DbtA@public.gmane.org>, Jann Horn <jann-XZ1E9jl8jIdeoWH0uzbU5w@public.gmane.org>
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"Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes:

> Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
>> +static bool setup_userns_sysctls(struct user_namespace *ns)
>> +{
>> +#ifdef CONFIG_SYSCTL
>> +	struct ctl_table *tbl;
>> +	setup_sysctl_set(&ns->set, &set_root, set_is_seen);
>> +	tbl = kmemdup(userns_table, sizeof(userns_table), GFP_KERNEL);
>> +	if (tbl) {
>> +		ns->sysctls = __register_sysctl_table(&ns->set, "userns", tbl);
>> +	}
>
> What happens if tbl is null due to oom?  Would it be better to just
> return false in that case here?

ns->sysctls is initialized to NULL and kfree(NULL) is a noop.
So I don't see any problems.

I admit it isn't a usual pattern for error handling.

>> +	if (!ns->sysctls) {
>> +		kfree(tbl);
>> +		retire_sysctl_set(&ns->set);
>> +		return false;
>> +	}
>> +#endif
>> +	return true;
>> +}

Eric