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Message-ID: <dcde302f-faa7-5e55-1e67-f8c7386119d4@suse.cz>
Date:   Thu, 24 Nov 2022 12:26:41 +0100
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Subject: Re: [PATCH 01/12] mm, slab: ignore hardened usercopy parameters when
 disabled
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To:     Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc:     Kees Cook <kees@kernel.org>, Christoph Lameter <cl@linux.com>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Pekka Enberg <penberg@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Matthew Wilcox <willy@infradead.org>, patches@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Kees Cook <keescook@chromium.org>
References: <20221121171202.22080-1-vbabka@suse.cz>
 <20221121171202.22080-2-vbabka@suse.cz>
 <206E0154-63A6-45CF-8E19-BD01B35AEF0B@kernel.org>
 <0058169a-1659-7ab1-edff-de9ebadcf236@suse.cz> <Y39Sq8vReXouviyn@hyeyoo>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <Y39Sq8vReXouviyn@hyeyoo>
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On 11/24/22 12:16, Hyeonggon Yoo wrote:
>>  	/* Fail closed on bad usersize of useroffset values. */
>> -	if (WARN_ON(!usersize && useroffset) ||
>> +	if (!IS_ENABLED(CONFIG_HARDENED_USERCOPY) ||
>> +	    WARN_ON(!usersize && useroffset) ||
>>  	    WARN_ON(size < usersize || size - usersize < useroffset))
>>  		usersize = useroffset = 0;
> 
> I think this change is no longer needed as slab_unmergeable()
> now does not check usersize when CONFIG_HARDENED_USERCOPY=n?

True, but the code here still follows by

if (!usersize)
    s = __kmem_cache_alias(name, size, align, flags, ctor);

So it seemed simplest just to leave it like that.