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SubjectRe: [Patch] lkdtm: avoid calling lkdtm_do_action() with spin lock held
On 02/01/2012 11:29 PM, Arnd Bergmann wrote:
> On Wednesday 01 February 2012, Cong Wang wrote:
>> On 01/31/2012 11:35 PM, Arnd Bergmann wrote:
>>> On Tuesday 31 January 2012, Cong Wang wrote:
>>>> @@ -323,14 +323,16 @@ static void lkdtm_do_action(enum ctype which)
>>>> }
>>>> case CT_WRITE_AFTER_FREE: {
>>>> size_t len = 1024;
>>>> - u32 *data = kmalloc(len, GFP_KERNEL);
>>>> + u32 *data = kmalloc(len, GFP_ATOMIC);
>>>>
>>>> kfree(data);
>>>> - schedule();
>>>> + udelay(100);
>>>> memset(data, 0x78, len);
>>>> break;
>>>> }
>>>
>>> I can't think of why the udelay would have any positive effect here,
>>> if the idea of the schedule was to let some other process allocate and
>>> use the memory.
>>
>>
>> Hmm, on SMP udelay on this CPU will give a chance to other CPU's to use
>> that memory, right?
>>
>
> There is a small chance for that, but it's much less likely than it would
> be using another process on the same CPU, plus it requires SMP.

Yeah, I updated this in [PATCH 2/2] lkdtm: avoid calling sleeping
functions in interrupt context.


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