Re: Bug creating USB endpoints in 2.6.20.x (kernel bug 8198)

On Thu, 3 May 2007, Tejun Heo wrote:

> Hello, Alan Stern.
> 
> Alan Stern wrote:
> >> The endpoint directory shown in the oops report does not exist if I'm not thrashing the box with
> >> winecfg. On Tejun Heo's suggestion, I put some debug code at the beginning of sysfs_release() to
> >> print a stack-dump and the kobject's path if the attr->owner field contains 0x6b6b6b6b or
> >> 0x5a5a5a5a poison:
> >>
> >> XXX debug trap owner=6b6b6b6b, path=/class/usb_endpoint/usbdev1.3_ep84
> >> XXX debug stack-dump
> >>  [<c018462a>] sysfs_release+0x70/0xa5
> >>  [<c0151837>] __fput+0x96/0x13c
> >>  [<c014f358>] filp_close+0x51/0x58
> >>  [<c0150351>] sys_close+0x70/0xa7
> >>  [<c0102bde>] sysenter_past_esp+0x5f/0x85
> >>  [<c0270033>] unix_create1+0xa2/0xee
> >>  =======================
> > 
> > This clearly indicates that something has been deallocated too early (or 
> > equivalently, used too late).
> 
> What has been filled with the 6b pattern here is struct attribute not
> some sysfs internal object.

Are you sure?

>  Does USB allocate struct attribute
> dynamically for any of its attributes?

No; it uses sysfs_create_group() with a static attribute group list.  I
don't know why it doesn't call device_add_group() -- maybe it was written
before that function existed.

You can see the code in drivers/usb/core/endpoint.c:usb_create_ep_files().

Alan Stern


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