linux-kernel - Re: [PATCH v2] mm, slub: emit the "free" trace report before freeing memory in kmem_cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <a0217bfe-87da-8f2a-6a40-edd061baad26@huawei.com>
Date:   Wed, 3 Nov 2021 11:41:26 +0800
From:   Yunfeng Ye <yeyunfeng@...wei.com>
To:     John Hubbard <jhubbard@...dia.com>, <cl@...ux.com>,
        <penberg@...nel.org>, <rientjes@...gle.com>,
        <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, <vbabka@...e.cz>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
CC:     <songmuchun@...edance.com>, <willy@...radead.org>,
        <wuxu.wu@...wei.com>, Hewenliang <hewenliang4@...wei.com>
Subject: Re: [PATCH v2] mm, slub: emit the "free" trace report before freeing
 memory in kmem_cache_free()



On 2021/11/3 2:37, John Hubbard wrote:
> On 11/2/21 04:43, Yunfeng Ye wrote:
>> After the memory is freed, it can be immediately allocated by other
>> CPUs, before the "free" trace report has been emitted. This causes
>> inaccurate traces.
>>
>> For example, if the following sequence of events occurs:
>>
>>      CPU 0                 CPU 1
>>
>>    (1) alloc xxxxxx
>>    (2) free  xxxxxx
>>                           (3) alloc xxxxxx
>>                           (4) free  xxxxxx
>>
>> Then they will be inaccurately reported via tracing, so that they appear
>> to have happened in this order:
>>
>>      CPU 0                 CPU 1
>>
>>    (1) alloc xxxxxx
>>                           (2) alloc xxxxxx
>>    (3) free  xxxxxx
>>                           (4) free  xxxxxx
>>
>> This makes it look like CPU 1 somehow managed to allocate mmemory that
> 
> 
> I see I created a typo for you, sorry about that: s/mmemory/memory/
> 
> But anyway, the wording looks good now. Please feel free to add:
> 
> Reviewed-by: John Hubbard <jhubbard@...dia.com>
> 
Ok, I will fix the typo in the v3 patch.

Thanks.

> 
> thanks,