Re: [RFC PATCH 1/1] mm/percpu.c: fix potential memory leakage for pcpu_embed_first_chunk()

[zijun_hu <zijun_hu@zoho.com>]

On 2016/9/30 16:43, Tejun Heo wrote:
> Hello,
> 
> On Fri, Sep 30, 2016 at 01:38:35AM +0800, zijun_hu wrote:
>> 1) the simpler way don't work because it maybe free many memory block twice
> 
> Right, the punched holes.  Forgot about them.  Yeah, that's why the
> later failure just leaks memory.
> 
>> 2) as we seen, pcpu_setup_first_chunk() doesn't cause a failure, it  return 0
>>    always or panic by BUG_ON(), even if it fails, we can conclude the allocated
>>    memory based on information recorded by it, such as pcpu_base_addr and many of
>>    static variable, we can complete the free operations; but we can't if we
>>    fail in the case pointed by this patch
> 
> So, being strictly correct doesn't matter that much here.  These
> things failing indicates that something is very wrong with either the
> code or configuration and we might as well trigger BUG.  That said,
> yeah, it's nicer to recover without leaking anything.
> 
>> 3) my test way is simple, i force "if (max_distance > VMALLOC_TOTAL * 3 / 4)"
>>    to if (1) and print which memory i allocate before the jumping, then print which memory
>>    i free after the jumping and before returning, then check whether i free the memory i 
>>    allocate in this function, the result is okay
> 
> Can you please include what has been discussed into the patch
> description?
> 
> Thanks.
> 
okayi 1/4 ? no problem

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