Re: [PATCH] PowerPC: kernel: memory access violation when rtas_data_bufcontents are more than 1026
From: Chen Gang
Date: Wed Apr 24 2013 - 03:41:45 EST
On 2013å04æ24æ 15:23, Vasant Hegde wrote:
> On 04/24/2013 12:33 PM, Chen Gang wrote:
>> On 2013å04æ24æ 14:28, Vasant Hegde wrote:
>>> On 04/23/2013 08:42 AM, Chen Gang wrote:
>>>> need set '\0' for 'local_buffer'.
>>>> SPLPAR_MAXLENGTH is 1026, RTAS_DATA_BUF_SIZE is 4096. so the
>>>> contents of
>>>> rtas_data_buf may truncated in memcpy.
>>>> if contents are really truncated.
>>>> the splpar_strlen is more than 1026. the next while loop
>>>> checking will
>>>> not find the end of buffer. that will cause memory access
>>> Per parameter length in ibm,get-system-parameter RTAS call is limited to
>>> 1026 bytes (1024 bytes of data + 2 bytes length). And 'rtas_data_buf'
>>> was set to 0 (first 1026 bytes) before call RTAS call. At the worst if
>>> we get junk in RTAS output length field helps to exit from the while
>>> loop. So I don't think we need this patch.
>> Is get-system-parameter return the NUL terminated string ? if so, it
>> will no issue (just like your discription).
> Length includes the length of the NULL. So (idx < splpar_strlen)
> is safe. IMO existing code is proper.
OK, since it is not an issue, I will try another patches for powerpc POWER7.
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