From: Oleg Nesterov <oleg@redhat.com>
To: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Roland McGrath <roland@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org,
Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH 1/2] task_struct cleanup: move binfmt field to mm_struct
Date: Tue, 28 Jul 2009 16:37:34 +0200 [thread overview]
Message-ID: <20090728143734.GA6664@redhat.com> (raw)
In-Reply-To: <4A6E98DC.5020200@ct.jp.nec.com>
On 07/28, Hiroshi Shimamoto wrote:
>
> Oleg Nesterov wrote:
> > (add Rusty)
> >
> > On 07/27, Hiroshi Shimamoto wrote:
> >> void set_binfmt(struct linux_binfmt *new)
> >> {
> >> - if (current->binfmt)
> >> - module_put(current->binfmt->module);
> >> + struct mm_struct *mm = current->mm;
> >> +
> >> + BUG_ON(!mm);
> >> + if (mm->binfmt)
> >
> > I am not sure we need this BUG_ON() above. If mm == NULL we will
> > have the same debug info after the crash.
>
> Ah, right. It will crash at accessing mm->binfmt and we'll get the
> same information. I didn't think seriously.
> BTW, now I noticed that it looks similar the security issue with
> NULL page mapping. If the kernel has the page mapping to NULL,
> it causes unstable behavior, no?
The kernel can't have NULL mapped. The task can, but in this case
it must have a valid ->mm != NULL.
IOW, if current->mm == NULL, current uses init_mm and thus NULL
can't be mapped.
Oleg.
next prev parent reply other threads:[~2009-07-28 14:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-10 8:42 [RFC 1/2] move binfmt filed to signal_struct Hiroshi Shimamoto
2009-07-10 8:43 ` [RFC 2/2] make binfmt module get and put per signal_struct Hiroshi Shimamoto
2009-07-22 20:23 ` [RFC 1/2] move binfmt filed to signal_struct Andrew Morton
2009-07-22 22:03 ` Roland McGrath
2009-07-23 16:18 ` Oleg Nesterov
2009-07-24 0:15 ` Hiroshi Shimamoto
2009-07-24 4:15 ` [PATCH 1/2] task_struct cleanup: move binfmt field to mm_struct Hiroshi Shimamoto
2009-07-24 4:17 ` [PATCH 2/2] task_struct cleanup: make binfmt module get and put per mm_struct Hiroshi Shimamoto
2009-07-24 16:14 ` [PATCH 1/2] task_struct cleanup: move binfmt field to mm_struct Oleg Nesterov
2009-07-27 0:27 ` Hiroshi Shimamoto
2009-07-27 16:59 ` Oleg Nesterov
2009-07-28 6:21 ` Hiroshi Shimamoto
2009-07-28 14:37 ` Oleg Nesterov [this message]
2009-07-30 0:42 ` [PATCH 0/1] " Hiroshi Shimamoto
2009-07-30 0:43 ` [PATCH 1/1] " Hiroshi Shimamoto
2009-07-30 17:55 ` Oleg Nesterov
2009-07-30 19:27 ` Roland McGrath
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