netdev - Re: [BUG] skge: a possible sleep-in-atomic bug in skge

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Message-ID: <772ac173-c52a-bd24-9b67-4bdfd932fdd1@gmail.com>
Date:   Thu, 14 Dec 2017 11:06:33 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     David Miller <davem@...emloft.net>, mlindner@...vell.com,
        shemminger@...l.org, shemminger@...ux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] skge: a possible sleep-in-atomic bug in skge_remove



On 2017/12/14 0:50, Stephen Hemminger wrote:
> On Wed, 13 Dec 2017 15:42:56 +0800
> Jia-Ju Bai <baijiaju1990@...il.com> wrote:
>
>> On 2017/12/13 13:18, Stephen Hemminger wrote:
>>> On Tue, 12 Dec 2017 20:57:01 -0500 (EST)
>>> David Miller <davem@...emloft.net> wrote:
>>>   
>>>> From: Stephen Hemminger <stephen@...workplumber.org>
>>>> Date: Tue, 12 Dec 2017 10:22:40 -0800
>>>>   
>>>>> On Tue, 12 Dec 2017 08:34:45 -0500 (EST)
>>>>> David Miller <davem@...emloft.net> wrote:
>>>>>       
>>>>>> From: Jia-Ju Bai <baijiaju1990@...il.com>
>>>>>> Date: Tue, 12 Dec 2017 16:38:12 +0800
>>>>>>       
>>>>>>> According to drivers/net/ethernet/marvell/skge.c, the driver may sleep
>>>>>>> under a spinlock.
>>>>>>> The function call path is:
>>>>>>> skge_remove (acquire the spinlock)
>>>>>>>     free_irq --> may sleep
>>>>>>>
>>>>>>> I do not find a good way to fix it, so I only report.
>>>>>>> This possible bug is found by my static analysis tool (DSAC) and
>>>>>>> checked by my code review.
>>>>>> This was added by:
>>>>>>
>>>>>> commit a9e9fd7182332d0cf5f3e601df3e71dd431b70d7
>>>>>> Author: Stephen Hemminger <shemminger@...tta.com>
>>>>>> Date:   Tue Sep 27 13:41:37 2011 -0400
>>>>>>
>>>>>>       skge: handle irq better on single port card
>>>>>>
>>>>>> I think the free_irq() can be moved below the unlock.
>>>>>>
>>>>>> Stephen, please take a look.
>>>>> The IRQ was being free twice.
>>>>> How did you see it, I really doubt any multi-port SKGE cards
>>>>> still exist.
>>>> He sees it by reading the code, please take a look at this
>>>> and move the free_irq() out of the spin locked section since
>>>> it can sleep.
>>> Thanks, I was hoping for some automated static analysis tool.
>> This bug was found by an automated static analysis tool named DSAC,
>> which is written by myself.
>> Then I manually checked driver source code, and finally sent the bug report.
> Thanks.
> Would it be possible to put tool in tools directory and then have
> it automated by kbuild robot?
Hi,

Thanks for your appreciation of my tool :)

I think it is possible. But before releasing, I need to improve it to 
solve some problems:
1. It produces some false positives and negatives. Thus I need 
developer's response and confirmation of my bug reports, to help me to 
improve my tool's accuracy.
2. It is based on Clang-3.2 (a LLVM-based compiler, not GCC), and some 
driver code cannot compile normally. Maybe I should re-implement my tool 
based on a recent Clang version.
3. Some software is needed when running my tool, thus as MySQL (maybe I 
directly can write to files, instead of database in the future) and 
Clang (Clang is necessary).

I think it may be difficult to directly put my tool in "tools" 
directory. But with some configuration, it is possible to run it 
automatically in a testing environment.
I also plan to open this tool in the future, after finishing the 
improvements :)


Thanks,
Jia-Ju Bai