linux-kernel - Possible NULL pointer dereference in m32r

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Date:	Mon, 1 Feb 2010 21:36:35 +0000
From:	Steve Kemp <kernel@...ve.org.uk>
To:	linux-kernel@...r.kernel.org
Subject: Possible NULL pointer dereference in m32r

   arch/m32r/kernel/smp.c contains the following code:

--
    preempt_disable();
    cpu_id = smp_processor_id();
    mmc = &mm->context[cpu_id];
    cpu_mask = mm->cpu_vm_mask;
    cpu_clear(cpu_id, cpu_mask);

#iffdef DEBUG_SMP
   if (!mm)
       BUG();
#endif
--

  mm might be NULL, but this would only be detected after it
 has been dereferenced, and only then if DEBUG_SMP is defined.

  I'd suggest changing to read something like this:

--
    if ( !mm )
        BUG();

    preempt_disable();
--

Steve
--
http://www.steve.org.uk/
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