linux-kernel - Re: NULL pointer at kset_find

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Date:	Wed, 03 Apr 2013 16:40:13 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	David Howells <dhowells@...hat.com>, CAI Qian <caiqian@...hat.com>
Cc:	dhowells@...hat.com, LKML <linux-kernel@...r.kernel.org>
Subject: Re: NULL pointer at kset_find_obj

David Howells <dhowells@...hat.com> writes:
> CAI Qian <caiqian@...hat.com> wrote:
>
>> Just booted the latest mainline,
>> 
>> [   35.217698] Request for unknown module key 'Magrathea: Glacier signing
>> key: 8b7774b08bc4ee9637073434c10f0823f6fbe523' err -11
>
> Can you check back earlier in the dmesg to see whether the kernel tried to
> load the key?  -11 is presumably -EAGAIN - in which case no such key was found
> (rather than there being a cached lookup failure which is what -ENOKEY would
> indicate).  It is possible that you encountered the key-not-yet-valid problem
> due to your h/w clock showing a value prior to the start date on the key.
>  
>> [   35.218511] BUG: unable to handle kernel paging request at ffffffffa03093f0 
>> [   35.218521] IP: [<ffffffff81304710>] kset_find_obj+0x30/0x80 
>> ...
>> [   35.218575] Call Trace: 
>> [   35.218583]  [<ffffffff810c827d>] load_module+0xb0d/0x1b00 
>> [   35.218587]  [<ffffffff81321880>] ? ddebug_proc_open+0xc0/0xc0 
>> [   35.218593]  [<ffffffff81628cd8>] ? page_fault+0x28/0x30 
>> [   35.218596]  [<ffffffff810c9347>] sys_init_module+0xd7/0x120 
>> [   35.218601]  [<ffffffff81630d59>] system_call_fastpath+0x16/0x1b 
>
> I think this bit should be waved in front of Rusty.  It looks like it might be
> a bug in error handling code.

It does look like it, but I can't see it.  The module code doesn't see
an error (presumably sig_enforce is false), so we continue processing
the module like normal.

Is the module getting corrupted somehow?  I don't think the signing
infrastructure is doing it...

Puzzled,
Rusty.
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