linux-kernel - Re: INFO: task hung in hub_port

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Date:   Wed, 22 Sep 2021 12:15:08 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Alan Stern <stern@...land.harvard.edu>,
        Hao Sun <sunhao.th@...il.com>, Shuah Khan <shuah@...nel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org,
        a.darwish@...utronix.de, johan@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        oneukum@...e.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: INFO: task hung in hub_port_init

Hi Hao Sun,

On 9/20/21 8:31 AM, Shuah Khan wrote:
> On 9/18/21 7:53 AM, Alan Stern wrote:
>> On Sat, Sep 18, 2021 at 10:17:26AM +0800, Hao Sun wrote:
>>> Alan Stern <stern@...land.harvard.edu> 于2021年9月18日周六 上午10:02写道：
>>>>
>>>> On Sat, Sep 18, 2021 at 09:56:52AM +0800, Hao Sun wrote:
>>>>> Hi Alan,
>>>>>
>>>>> Alan Stern <stern@...land.harvard.edu> 于2021年9月13日周一 下午9:55写道：
>>>>>>
>>>>>> On Mon, Sep 13, 2021 at 11:13:15AM +0800, Hao Sun wrote:
>>>>>>> Hello,
>>>>>>>
>>>>>>> When using Healer to fuzz the Linux kernel, the following crash was triggered.
>>>>>>>
>>>>>>> HEAD commit: ac08b1c68d1b Merge tag 'pci-v5.15-changes'
>>>>>>> git tree: upstream
>>>>>>> console output:
>>>>>>> https://drive.google.com/file/d/1ZeDIMe-DoY3fB32j2p5ifgpq-Lc5N74I/view?usp=sharing
>>>>>>> kernel config: https://drive.google.com/file/d/1qrJUXD8ZIeAkg-xojzDpp04v9MtQ8RR6/view?usp=sharing
>>>>>>> Syzlang reproducer:
>>>>>>> https://drive.google.com/file/d/1tZe8VmXfxoPqlNpzpGOd-e5WCSWgbkxB/view?usp=sharing
>>>>>>> Similar report:
>>>>>>> https://groups.google.com/g/syzkaller-bugs/c/zX55CUzjBOY/m/uf91r0XqAgAJ
>>>>>>>
>>>>>>> Sorry, I don't have a C reproducer for this crash but have a Syzlang
>>>>>>> reproducer. Also, hope the symbolized report can help.
>>>>>>> Here are the instructions on how to execute Syzlang prog:
>>>>>>> https://github.com/google/syzkaller/blob/master/docs/executing_syzkaller_programs.md
>>>>>>>
>>>>>>> If you fix this issue, please add the following tag to the commit:
>>>>>>> Reported-by: Hao Sun <sunhao.th@...il.com>
>>>>>>
>>>>>> There's not much hope of finding the cause of a problem like this
>>>>>> without seeing the kernel log.
>>>>>>
>>>>>
>>>>> Healer found another Syzlang prog to reproduce this task hang:
>>>>> https://paste.ubuntu.com/p/HCNYbKJYtx/
>>>>>
>>>>> Also here is a very simple script to execute the reproducer:
>>>>> https://paste.ubuntu.com/p/ZTGmvFSP6d/
>>>>>
>>>>> The `syz-execprog` and `syz-executor` are needed, so please build
>>>>> Syzkaller first before running the script.
>>>>> Hope this can help to find the root cause of the problem.
>>>>
>>>> I don't have time to install and figure out how to use Healer and
>>>> Syzkaller.  But if you run the reproducer and post the kernel log,
>>>> I'll take a look at it.
>>>>
>>>
>>> Just executed the reproducer, here is the full log:
>>> https://paste.ubuntu.com/p/x43SqQy8PX/
>>
>> The log indicates that the problem is related to the vhci-hcd driver
>> somehow.  I don't know why those "Module has invalid ELF structures"
>> errors keep appearing, starting in line 1946 of the log.
>>

Can you send me your config? This message is rather odd.

[   82.249631][ T6679] Module has invalid ELF structures

It is right below:
[   82.248529][ T6679] vhci_hcd vhci_hcd.0: Device attached

or

[   83.860819][ T6710] vhci_hcd vhci_hcd.0: port 0 already used

My guess is this isn't the vhci_hcd module that gets loaded at this
point when we see this message, but another module that gets loaded
when vhci_hcd initiates probe after device attach. Note that vhci_hcd
is loaded earlier.

It is possible, the hung task might be related to load_module()
failure. Unfortunately load_module() doesn't print elf_validity_check()
error.

Would you be able to add this patch and run the reproducer again?


--------------------------------------------------------------------
diff --git a/kernel/module.c b/kernel/module.c
index 40ec9a030eec..02f758b04f05 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3941,7 +3941,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
          */
         err = elf_validity_check(info);
         if (err) {
-               pr_err("Module has invalid ELF structures\n");
+               pr_err("Module has invalid ELF structures error (%ld)\n",
+                       err);
                 goto free_copy;
         }

--------------------------------------------------------------------

thanks,
-- Shuah