Messages in this thread | | | Date | Fri, 16 Nov 2007 01:34:54 +0100 | From | "Jesper Juhl" <> | Subject | Re: mm_release() call in exit_mm() looks dangerous |
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On 13/11/2007, Jeremy Fitzhardinge <jeremy@goop.org> wrote: > Jesper Juhl wrote: > > In kernel/exit.c we have this code : > > > > static void exit_mm(struct task_struct * tsk) > > { > > struct mm_struct *mm = tsk->mm; > > > > mm_release(tsk, mm); > > if (!mm) > > return; > > ... > > > > > > But, mm_release() may dereference it's second argument ('mm'), so > > shouldn't we be doing the "!mm" test *before* we call mm_release() and > > not after? > > I don't know the mm code well enough to be able to tell if some of the > > other stuff mm_release does needs to be done always and the mm > > dereference can't actually happen, but maybe someone else who knows > > the code better can tell... In any case, what's currently there looks > > a little shaky.. > > > > Yeah, it looks wrong. mm_release() calls deactivate_mm() as its first > act, which could well dereference mm (though it often doesn't). > So, whould simply moving the !mm check up as the first in the function be an appropriate way to deal with this?
-- Jesper Juhl <jesper.juhl@gmail.com> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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