[B.A.T.M.A.N.] [PATCH] batman-adv-kernelland: Fix memory corruption bug

Simon Wunderlich simon.wunderlich at s2003.tu-chemnitz.de
Fri Dec 5 19:51:31 UTC 2008


Hey Scott,

On Fri, Dec 05, 2008 at 11:40:30PM +1300, Scott Raynel wrote:
> Hi Simon,
> 
> On 5/12/2008, at 12:35 AM, Simon Wunderlich wrote:
> 
> >Hey Scott,
> >
> >thank you very much for the fix! Can you confirm if this bug is  
> >related
> >to https://dev.open-mesh.net/batman/ticket/86 ?
> >This bug has very likely been caused by a memory corruption, but i
> >couldn´t find where. (i have not experienced any kernel panics by  
> >this
> >however ...).
> 
> 
> It is quite possible that they are related. The slab error states that  
> a memory allocation was overwritten - the same problem as my patch  
> fixed. However, I can't confirm whether it is the same memory  
> allocation or a different one. The stack trace I got specifically  
> mentioned the kfree() in send_own_packet(), whereas this stack trace  
> does not.
> 
> Is that bug easily reproducible? It will be a couple of days before I  
> can try to look at it.

Yep, it was quite easy: just turn it on and off a few times. (echo
device and nothing into /proc/net/batman-adv/interfaces). The warning
appeared after 10 times in my qemu instance. No crash, only this warning.
> 
> Also, the stack trace is confusing as it appears to indicate a kfree()  
> within hardif_min_mtu(), which I can't find :)

That's the problem, that is what confused me at this point. :/

> 
> I'll try to do some stress testing of the module with the slab  
> debugger turned on for a while and see what happens.

Sounds great. Thanks for you hard work. :)

best regards,
	Simon
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