Can't cleanly unload driver

[Eric Fowler]

Still working on this. Here is some dmesg spew:

[  514.245846] foobar: module verification failed: signature and/or
required key missing - tainting kernel
[  514.245937] kobject: 'foobar' (f7f060c8): kobject_add_internal: parent:
'module', set: 'module'
[  514.245951] kobject: 'holders' (f5ff3d40): kobject_add_internal: parent:
'foobar', set: '<NULL>'
[  514.245981] kobject: 'notes' (f2d25f80): kobject_add_internal: parent:
'foobar', set: '<NULL>'
[  514.245987] kobject: 'foobar' (f7f060c8): kobject_uevent_env
[  514.245998] kobject: 'foobar' (f7f060c8): fill_kobj_path: path =
'/module/foobar'

So it looks like kernel validation is failing. I have printk's in my init
fxn that are never turning up in /var/log/messages, until, weirdly, AFTER I
remove the device:

<insmod device>
Dec 30 09:43:03 localhost kernel: [  514.245846] foobar: module
verification failed: signature and/or required key missing - tainting kernel
Dec 30 09:43:16 localhost fprintd[1085]: ** Message: No devices in use, exit

<rmmod device>
Dec 30 09:45:53 localhost kernel: [  514.249323] foobar: got device number
248, minor is 0   <<<<----THIS IS IN init() fxn
Dec 30 09:45:53 localhost kernel: [  684.102912] unregister_chrdev(248)
called for foobar<7>[  684.102927] kobject: '(null)' (f7f06220):
kobject_cleanup, parent   (null)

<insmod>
insmod: ERROR: could not insert module ./foobar.ko: Device or resource busy








On Fri, Dec 27, 2013 at 9:13 PM, <Valdis.Kletnieks at vt.edu> wrote:

> On Fri, 27 Dec 2013 19:33:50 -0800, Eric Fowler said:
>
> > I suspect I am doing something wrong in the code with
> > register/unregister_chrdev(), but I have been over that code a million
> > times. It looks fine.
> >
> > Now:
> > insmod the device, OK
> > rmmod the device, OK
> > Check /proc/devices , device # is present
> > insmod the device again, fails with ERROR: could not insert module
> > ./foobar.ko: Device or resource busy
>
> It does smell like an unregister issue.  You may want to try adding
> printk() calls to print out the return code from register and unregister.
> I'm willing to bet that (a) the unegister is failing because somebody
> still has a reference on the device, and (b) the second register call fails
> because the device already exists, causing your module_init() to bail out.
>
> The fun is that you may not have taken a reference on the device directly
> yourself - you may have called some other get_foo() that ends up taking an
> implicit reference under the covers, causing issues when you fail to call
> put_foo() at the right place...
>



-- 
cc:NSA
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