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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v7 0/3] mm/slub: extend redzone check for kmalloc objects Content-Language: en-US To: Feng Tang , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Dmitry Vyukov , Andrey Konovalov , Kees Cook Cc: Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com References: <20221021032405.1825078-1-feng.tang@intel.com> From: Vlastimil Babka In-Reply-To: <20221021032405.1825078-1-feng.tang@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668154595; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; 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dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=eyv34fHR; dmarc=none; spf=pass (imf01.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Stat-Signature: ypqmjuiyzkmdegmgoaujnx4hymrxji45 X-HE-Tag: 1668154594-89561 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/21/22 05:24, Feng Tang wrote: > kmalloc's API family is critical for mm, and one of its nature is that > it will round up the request size to a fixed one (mostly power of 2). > When user requests memory for '2^n + 1' bytes, actually 2^(n+1) bytes > could be allocated, so there is an extra space than what is originally > requested. > > This patchset tries to extend the redzone sanity check to the extra > kmalloced buffer than requested, to better detect un-legitimate access > to it. (dependson SLAB_STORE_USER & SLAB_RED_ZONE) > > The redzone part has been tested with code below: > > for (shift = 3; shift <= 12; shift++) { > size = 1 << shift; > buf = kmalloc(size + 4, GFP_KERNEL); > /* We have 96, 196 kmalloc size, which is not power of 2 */ > if (size == 64 || size == 128) > oob_size = 16; > else > oob_size = size - 4; > memset(buf + size + 4, 0xee, oob_size); > kfree(buf); > } Sounds like a new slub_kunit test would be useful? :) doesn't need to be that exhaustive wrt all sizes, we could just pick one and check that a write beyond requested kmalloc size is detected? Thanks!