Does Linux process exist information leakage?

[SaNtosh kuLkarni]

am not sure about my answer but regarding kmalloc if i am going out of
context ..but when u do a* kmalloc it doesnt clear *the memory obtained and
still holds the prvious contents...what happens in that case ..and as far
as i know when u take the case of reparenting ....during process
termination  exit_mm() is called to release the mm_struct held by this
process. If no other process
is using this address space, if the address space is not shared―the
kernel then destroys it and also there is the senario of zombie exit...i
mean PDT remains after parent exits....


2012/1/19 夏业添 <summerxyt at gmail.com>

> Thanks！
>
> It seems that the function do_page_fault() will finally call
> fast_clear_page()<http://lxr.oss.org.cn/plain/source/arch/x86/lib/mmx_32.c#L125>
>  or slow_zero_page()<http://lxr.oss.org.cn/plain/source/arch/x86/lib/mmx_32.c#L336> to
> zero a new physical page for a process. So calling malloc() cannot get a
> page used by another process which is dead already.
>
> The assemble language is difficult to me, so please tell me if I am wrong.
>
> 2012/1/18 Fredrick <fjohnber at zoho.com>
>
>> When you malloc a memory or mmap a MAP_ANON memory, it is virtually
>> allocated. When you read or write to it, the process takes a page fault.
>> The page fault handler zeroes those memory and hands it to the process. So
>> I think there is no leak.
>>
>> -Fredrick
>>
>>
>> On 01/11/2012 04:53 AM, 夏业添 wrote:
>>
>>> Hi,
>>>    My tutor asked me to test whether one process leaves information in
>>> memory after it is dead. I tried to search some article about such thing
>>> on the Internet but there seems to be no one discuss about it. And after
>>> that, I tried to write some program in the User Mode to test it, using
>>> fork() to create lots of processes and filling char 'a' into a 102400
>>> bytes char array in each process. Then I used malloc() to get some
>>> memory to seek char 'a' in a new one process or many new processes, but
>>> failed. All memory I malloced was full of zero.
>>>    As the man page of malloc said:"The memory is not initialized", I
>>> believe that the memory which was got by malloc() could be used by other
>>> process, and therefor information leakage exists. But how can I test it?
>>> Or where can I get related information?
>>>    Thanks!
>>>
>>>
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>>
>>
>>
>
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-- 
*Regards,
Santosh Kulkarni*
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