Re: [PATCH] kobject_uevent: Fix OOB access within zap_modalias_env()

[quic_zijuhu]

On 5/24/2024 2:56 PM, Greg KH wrote:
> On Fri, May 24, 2024 at 01:34:49PM +0800, quic_zijuhu wrote:
>> On 5/24/2024 1:21 PM, Greg KH wrote:
>>> On Fri, May 24, 2024 at 01:15:01PM +0800, quic_zijuhu wrote:
>>>> On 5/24/2024 12:33 PM, Greg KH wrote:
>>>>> On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
>>>>>> zap_modalias_env() wrongly calculates size of memory block
>>>>>> to move, so maybe cause OOB memory access issue, fixed by
>>>>>> correcting size to memmove.
>>>>>
>>>>> "maybe" or "does"?  That's a big difference :)
>>>>>
>>>> i found this issue by reading code instead of really meeting this issue.
>>>> this issue should be prone to happen if there are more than 1 other
>>>> environment vars.
>>>
>>> But does it?  Given that we have loads of memory checkers, and I haven't
>>> ever seen any report of any overrun, it would be nice to be sure.
>>>
>> yes. if @env includes env vairable MODALIAS and  more than one other env
>> vairables. then (env->buflen - len) must be greater that actual size of
>> "target block" shown previously, so the OOB issue must happen.
> 
> Then why are none of the tools that we have for catching out-of-bound
> issues triggered here?  Are the tools broken or is this really just not
> ever happening?  It would be good to figure that out...
> 
don't know why. perhaps, need to report our case to expert of tools.
> thanks,
> 
> greg k-h