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Fri, 14 Jul 2023 08:01:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id KeAdEMwAsWQDSAAAMHmgww (envelope-from ); Fri, 14 Jul 2023 08:01:16 +0000 Message-ID: <7c33a6c3-4ded-e0e4-820d-ffc337da9800@suse.cz> Date: Fri, 14 Jul 2023 10:01:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 2/2] mm/slub: remove freelist_dereference() From: Vlastimil Babka To: Kees Cook Cc: Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Roman Gushchin , linux-mm@kvack.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, Matteo Rizzo , Jann Horn , Andrey Konovalov , Marco Elver , Alexander Potapenko , kasan-dev@googlegroups.com, linux-hardening@vger.kernel.org References: <20230711134623.12695-3-vbabka@suse.cz> <20230711134623.12695-4-vbabka@suse.cz> <202307110917.DEED145F0@keescook> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 434F3C0009 X-Stat-Signature: bszf3adoofuaz5y37rcpju55gwfqa5nf X-Rspam-User: X-HE-Tag: 1689321678-223166 X-HE-Meta: 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 n/guiThx t/qzcRsfF87OaBT2LDXWYdn1DJFip0sAehhd3qXXN28V7fLPX3OwRsLc1ErAygURM7q4NNcAxu1r39lHi/1JDy8YdYwCSySqgak09ykDQ9a9JktblLqsI+UOfwZ+rKAgATN0L+tj/O4z6qMt6iwQD6V7K5XsJt572bMwXbF49CMoKEVI47KZoaK08aoYQpdjeK48q4IDpz+FgVbi2SqUlE9VBqjcaiJikZciwnbmpZsNYXbkFV8MVjEa84OpgYdIpKynYNe1S1yLKLhvbyvyj4Hncb6+7heUwt03QYJhIezE7uarziXfSGvYmdp8wEqz7hkHSRpYM2qkqTXRNtI3CFZ0ErGzPFCbDYAMyFHo0FhgKXX5d+6Mo1PB5OQ== 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 7/13/23 09:44, Vlastimil Babka wrote: > On 7/11/23 18:21, Kees Cook wrote: >> On Tue, Jul 11, 2023 at 03:46:25PM +0200, Vlastimil Babka wrote: >>> >>> #ifndef CONFIG_SLUB_TINY >>> -- >>> 2.41.0 >>> >> >> I like reducing the complexity here, but I find dropping the "object" >> reassignment makes this a bit harder to read. What about: > > Alright. > >> object = kasan_reset_tag(object); >> unsigned long ptr_addr = (unsigned long)object + s->offset; >> freeptr_t p = *(freeptr_t *)(ptr_addr); > > Are we really so benevolent with declaration-after-statement now? :) I've left the declarations separate for now so it's similar to get_freepointer_safe(). Pushed the result to slab/for-6.6/cleanup and for-next. Thanks for the reviews! >> return freelist_ptr_decode(s, p, ptr_addr); >> >> ? >> >> They're the same result, so either way: >> >> Acked-by: Kees Cook >> >