linux-kernel - Re: [PATCH] sys_waitid: return -EFAULT for NULL

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Date:	Wed, 14 Jan 2009 12:14:20 +1300
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Roland McGrath" <roland@...hat.com>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"kernel list" <linux-kernel@...r.kernel.org>,
	"Ulrich Drepper" <drepper@...hat.com>,
	"Vegard Nossum" <vegard.nossum@...il.com>,
	"linux-man@...r.kernel.org" <linux-man@...r.kernel.org>
Subject: Re: [PATCH] sys_waitid: return -EFAULT for NULL

On Wed, Jan 14, 2009 at 11:49 AM, Roland McGrath <roland@...hat.com> wrote:
> It's always been invalid to call waitid() with a NULL pointer.  It was an
> oversight that it was allowed (and acts like a wait4() call instead).
>
> Signed-off-by: Roland McGrath <roland@...hat.com>

Modulo the observation that this change will break any Linux-specific
application that violate POSIX.1's requirement that infop not be NULL
(*), and rely on the existing Linux behavior for
waitd(idtype,id,NULL,options):

Acked-by: Michael Kerrisk <mtk.manpages@...il.com>

(*) It seems unlikely that such applications exist, and we really
should make this change for POSIX.1 conformance.

> ---
>  kernel/exit.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/exit.c b/kernel/exit.c
> index c7740fa..fa25790 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1760,6 +1760,8 @@ asmlinkage long sys_waitid(int which, pid_t upid,
>        enum pid_type type;
>        long ret;
>
> +       if (unlikely(!infop))
> +               return -EFAULT;
>        if (options & ~(WNOHANG|WNOWAIT|WEXITED|WSTOPPED|WCONTINUED))
>                return -EINVAL;
>        if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
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