linux-kernel - Re: [PATCH] argv_split: Return NULL if argument contains nonon-whitespace.

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Message-ID: <20130915162641.GA13344@redhat.com>
Date:	Sun, 15 Sep 2013 18:26:41 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	viro@...iv.linux.org.uk, rostedt@...dmis.org, fweisbec@...il.com,
	mingo@...hat.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] argv_split: Return NULL if argument contains
	nonon-whitespace.

On 09/15, Tetsuo Handa wrote:
>
> Oleg Nesterov wrote:
> > > upon core dump because helper_argv[0] == NULL at
> > >
> > >   helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
> > >   call_usermodehelper_setup(helper_argv[0], ...);
> >
> > Are you sure? See above.
> >
>
> Yes, I'm sure.

I thougt you meant that call_usermodehelper_setup() crashes. "See above"
means that afaics it should crash in do_filp_open().

> execve(NULL) from user space is safe,

because it never does do_execve(NULL),

> but
> do_execve(NULL) from kernel space is not safe.

Yes, this is clear.

> > Perhaps
> >
> > 	--- x/kernel/kmod.c
> > 	+++ x/kernel/kmod.c
> > 	@@ -571,6 +571,9 @@ int call_usermodehelper_exec(struct subp
> > 		DECLARE_COMPLETION_ONSTACK(done);
> > 		int retval = 0;
> >
> > 	+	if (!sub_info->path)
> > 	+		return -EXXX;
> > 	+
> > 		helper_lock();
> > 		if (!khelper_wq || usermodehelper_disabled) {
> > 			retval = -EBUSY;
> >
> > ?
> >
>
> I'm OK with that.

OK,

Oleg.

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