linux-kernel - Re: [PATCH 5/5] Move alloc_pid call to copy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070717133430.GA214@tv-sign.ru>
Date:	Tue, 17 Jul 2007 17:34:30 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	sukadev@...ibm.com
Cc:	Andrew Morton <akpm@...l.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Cedric Le Goater <clg@...ibm.com>,
	Dave Hansen <haveblue@...ibm.com>,
	Serge Hallyn <serue@...ibm.com>,
	Herbert Poetzel <herbert@...hfloor.at>,
	Pavel Emelianov <xemul@...nvz.org>,
	Linux Containers <containers@...ts.osdl.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] Move alloc_pid call to copy_process

On 07/16, sukadev@...ibm.com wrote:
>
> Oleg Nesterov [oleg@...sign.ru] wrote:
> | 
> | Could you please give more details why we need this change?
> 
> Well, with multiple pid namespaces, we may need to allocate a new
> 'struct pid_namespace' if the CLONE_NEWPID flag is specified. And
> as a part of initializing this pid_namespace, we need the 'task_struct'
> that will be the reaper of the new pid namespace.
> 
> And this task_struct is allocated in copy_process(). So we could
> still alloc_pid() in do_fork(), as we are doing currently and set
> the reaper of the new pid_namespace later in copy_process(). But
> that seemed to complicate error handling and add checks again in
> copy_process() for the CLONE_NEWPID.

OK, thanks.

> 
> | Even if we really need this, can't we do these checks in copy_process() ?
> 
> We could and I did have a check in copy_process() in one of my earlier
> versions to Containers@ list.  We thought it cluttered copy_process() a
> bit.

Yes, but having the "pid == &init_struct_pid" in free_pid() is imho worse,

>  	container_exit(p, container_callbacks_done);
>  	delayacct_tsk_free(p);
> +	free_pid(pid);
> +bad_fork_put_binfmt_module:
> [...snip...]
> @@ -206,6 +206,10 @@ fastcall void free_pid(struct pid *pid)
>  	/* We can be called with write_lock_irq(&tasklist_lock) held */
>  	unsigned long flags;
>  
> +	/* check this here to keep copy_process() cleaner */
> +	if (unlikely(pid == &init_struct_pid))
> +		return;
> +

Wouldn't it better if copy_process()'s error path does

	if (pid != &init_struct_pid)
		free_pid(pid);

instead? OK, "cleaner" is a matter of taste, but from the perfomance POV
this would be better, even if not noticable.

Oleg.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/