linux-kernel - Re: [PATCH] mm/slub: Add slub_debug option to panic on memory corruption

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Date:   Tue, 9 Mar 2021 20:12:53 +0200
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     Christoph Lameter <cl@...two.de>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, vbabka@...e.cz,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        corbet@....net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: Add slub_debug option to panic on memory
 corruption

Hi Christoph,

Thanks for the comments!

On 3/9/21 16:56, Christoph Lameter wrote:
> On Tue, 9 Mar 2021, Georgi Djakov wrote:
> 
>> Being able to stop the system immediately when a memory corruption
>> is detected is crucial to finding the source of it. This is very
>> useful when the memory can be inspected with kdump or other tools.
> 
> Hmmm.... ok.

The idea is to be able to collect data right after the corruption is
detected, otherwise more data might be corrupted and tracing becomes
more difficult.

> 
>>   static void restore_bytes(struct kmem_cache *s, char *message, u8 data,
>>   						void *from, void *to)
>>   {
>> +	if (slub_debug & SLAB_CORRUPTION_PANIC)
>> +		panic("slab: object overwritten\n");
>>   	slab_fix(s, "Restoring 0x%p-0x%p=0x%x\n", from, to - 1, data);
>>   	memset(from, data, to - from);
>>   }
> 
> Why panic here? This should only be called late in the bug reporting when
> an error has already been printed.

This is called by both slab_pad_check() and check_bytes_and_report(), so it
seemed like a common place where i could put the panic(). I can move it to
the caller functions instead, if that's preferred.

Thanks,
Georgi