linux-kernel - Re: Crash with kfree(null) on MacBook? kobject_set_name

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Date:	Mon, 11 Apr 2011 19:28:34 +0200
From:	Rafał Miłecki <zajec5@...il.com>
To:	Bob Copeland <me@...copeland.com>,
	Andy Botting <andy@...ybotting.com>,
	Arend van Spriel <arend@...adcom.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Crash with kfree(null) on MacBook? kobject_set_name_vargs

I just got report from Arend that he's hitting the same issue. I've no
idea what's wrong with my dev_set_name call. Should I pre-init struct
dev somehow? Before calling dev_set_name on it?

W dniu 10 kwietnia 2011 23:28 użytkownik Bob Copeland
<me@...copeland.com> napisał:
> 2011/4/10 Rafał Miłecki <zajec5@...il.com>:
>> I'm writing new axi bus driver and one of the early testers reported
>> it crashing for him. Andy is using MacBook and backtrace+debugging
>> pretty clearly point to kfree being called on null string.
>
>> bcopeland on #linux-wireless suggested turning on SLAB or SLUB. Is
>> this going to provide some interesting info?
>
> To be precise, I said slab or slub _debugging_.  The reason I said
> this is that often a crash on kfree() is due to memory corruption.
> Many places in the kernel rely on kfree(NULL) being a safe operation,
> so it's likely something more than that.  SL?B debugging adds
> poisoning and corresponding checks that detect several kinds of
> corruption like buffer overruns, use-after-free, etc.
>
> The other thing you can do is get the disassembly of the Code portion
> for your oops and match it up with specific C code, look at the
> register file in the oops and match that up with variable names, and
> work backwards to figure out which pointers are broken.  Sometimes
> this can be enlightening, like if a pointer has ascii values, or is a
> small number (0 + some struct offset).

Andy, Arend: I'm not sure if someone will have straight idea whats
wrong with my code. Could you try this SL?B debugging maybe?

-- 
Rafał
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