Re: BUG triggers running lsof

["K.R. Foley" <kr@cybsft.com>]

On 2020-11-20 15:13, Randy Dunlap wrote:
> On 11/20/20 12:59 PM, K.R. Foley wrote:
>> 
>> 
>> 
>> On 2020-11-20 13:51, Jeff Moyer wrote:
>>> Randy Dunlap <rdunlap@infradead.org> writes:
>>> 
>>>> On 11/20/20 11:16 AM, K.R. Foley wrote:
>>>>> I have found an issue that triggers by running lsof. The problem is
>>>>> reproducible, but not consistently. I have seen this issue occur on
>>>>> multiple versions of the kernel (5.0.10, 5.2.8 and now 5.4.77). It
>>>>> looks like it could be a race condition or the file pointer is 
>>>>> being
>>>>> corrupted. Any pointers on how to track this down? What additional
>>>>> information can I provide?
>>>> 
>>>> Hi,
>>>> 
>>>> 2 things in general:
>>>> 
>>>> a) Can you test with a more recent kernel?
>>>> 
>>>> b) Can you reproduce this without loading the proprietary & 
>>>> out-of-tree
>>>> kernel modules?  They should never have been loaded after bootup.
>>>> I.e., don't just unload them -- that could leave something bad 
>>>> behind.
>>> 
>>> Heh, the EIP contains part of the name of one of the modules:
>>> 
>>>> 
>>>>> [ 8057.297159] BUG: unable to handle page fault for address: 
>>>>> 31376f63
>>>                                                                 
>>> ^^^^^^^^
> 
> Thanks for noticing that, Jeff.  I should have seen it.
> 
>>>>> [ 8057.297219] Modules linked in: ITXico7100Module(O)
>>>                                          ^^^^
>> 
>> Perhaps this is a dumb question, but how could this happen?
> 
> 
> We don't know what is in that loadable kernel module, so we can't
> give a definitive answer to your question, other than it's buggy.
> Or maybe it was just written for an older kernel version.
> Or a kernel with different build options/settings.

I am starting to look at this now. It was written for an older kernel by 
someone else. Thank you for the tips.

> 
> Have you contacted IT support?
> 
> It would (will) be interesting to see if you can reproduce the problem
> without these modules being loaded...
> I kind of doubt it, but if it does still fail, it will give us 
> something
> to look at.

Knowing a little more now. I doubt it will be reproducible without the 
module.

-- 
Regards,
K.R. Foley