From: Ingo Molnar <mingo@elte.hu>
To: WANG Cong <xiyou.wangcong@gmail.com>
Cc: linux-kernel@vger.kernel.org, gvaughan@jpl.nasa.gov,
akpm@osdl.org, jeremy@goop.org
Subject: Re: [PATCH] Fix check after use in kernel/exit.c
Date: Mon, 10 Mar 2008 10:13:21 +0100 [thread overview]
Message-ID: <20080310091321.GA9452@elte.hu> (raw)
In-Reply-To: <20080310.162351.21322673.xiyou.wangcong@gmail.com>
* WANG Cong <xiyou.wangcong@gmail.com> wrote:
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -583,8 +583,6 @@ static void exit_mm(struct task_struct * tsk)
> struct mm_struct *mm = tsk->mm;
>
> mm_release(tsk, mm);
> - if (!mm)
> - return;
> @@ -464,6 +464,8 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
> {
> struct completion *vfork_done = tsk->vfork_done;
>
> + if (!mm)
> + return;
> /* Get rid of any cached register state */
> deactivate_mm(tsk, mm);
no, this is buggy in the same way - we wont do a deactivate_mm() for
kernel threads. The check should be left alone in exit_mm(), we should
at most add a check for NULL mm to this place:
if (tsk->clear_child_tid
&& !(tsk->flags & PF_SIGNALED)
&& atomic_read(&mm->mm_users) > 1) {
but ... can mm in fact ever be NULL if tsk->clear_child_tid is set?
Ingo
prev parent reply other threads:[~2008-03-10 9:13 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-08 8:11 [PATCH] Fix check after use in kernel/exit.c WANG Cong
2008-03-08 8:36 ` Ingo Molnar
2008-03-08 8:53 ` Ingo Molnar
2008-03-08 8:58 ` WANG Cong
2008-03-09 11:48 ` Ingo Molnar
2008-03-10 8:23 ` WANG Cong
2008-03-10 9:13 ` Ingo Molnar [this message]
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