linux-kernel - Re: Oops in make_class_name in 2.6.22.1 on Fedora

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Date:	Mon, 22 Oct 2007 18:06:46 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Greg KH <greg@...ah.com>, Pete Zaitcev <zaitcev@...hat.com>,
	linux-usb-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, Matthew Wilcox <matthew@....cx>
Subject: Re: Oops in make_class_name in 2.6.22.1 on Fedora

On 09/11/2007 11:11 AM, Alan Stern wrote:
>>>
>>> I do not seem to be able to find an answer, sorry.
>>> Do you happen to remember if this was fixed after 2.6.22.1:
>>>
>>> localhost kernel: EIP is at make_class_name+0x27/0x7a
>>> localhost kernel:  [<c05586f1>] class_device_del+0x97/0x119
>>> localhost kernel:  [<c055877b>] class_device_unregister+0x8/0x10
>>> localhost kernel:  [<e08735f4>] __scsi_remove_device+0x1d/0x60 [scsi_mod]
>>> localhost kernel:  [<e08711ae>] scsi_forget_host+0x2d/0x4a [scsi_mod]
>>> localhost kernel:  [<e086c49c>] scsi_remove_host+0x65/0xd5 [scsi_mod]
>>> localhost kernel:  [<e0e76775>] storage_disconnect+0xe/0x16 [usb_storage]
>>> localhost kernel:  [<c056f8b8>] usb_unbind_interface+0x44/0x85
>>> localhost kernel:  [<c0557df7>] __device_release_driver+0x6e/0x8b
>>>
>>> Obviously a known bug but all I see is users reporting it. In my case
>>> it's this:
>>>  https://bugzilla.redhat.com/show_bug.cgi?id=253424
>>> I saw Alan giving it a try here:
>>>  http://lkml.org/lkml/2007/7/12/259
>> I think this was a scsi problem that has been fixed, but don't really
>> remember the exact commit.
> 
> Yes.  There are some bugs in the SCSI async-scanning code, and there is
> a patch to fix them:
> 
> http://git.kernel.org/?p=linux/kernel/git/jejb/scsi-misc-2.6.git;a=commit;h=a93a091df8232fad60867d41fbc3be855a0b78f2
> 
> It is scheduled for 2.6.24.  For now, people can work around the bug by 
> disabling CONFIG_SCSI_SCAN_ASYNC.
> 

The bug still happens with that patch applied and CONFIG_SCSI_SCAN_ASYNC
enabled. In the marked line, class_dev->class->name is NULL and this causes
the oops in make_class_name().


static void remove_deprecated_class_device_links(struct class_device *class_dev)
{
        char *class_name;

        if (!class_dev->dev)
                return;

===>>   class_name = make_class_name(class_dev->class->name, &class_dev->kobj);
        if (class_name)
                sysfs_remove_link(&class_dev->dev->kobj, class_name);
        kfree(class_name);
}

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