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bh=eQD4Br/ZzkU5aWA9puuXt04qjFbGSUKuou34lXjuW3Q=; b=Zq04zdamaPjOhsuCl+Afz98X/bFz/Q4bH/eoiKIUxr1xa1vQZBgEQKcm+Uq1Cm9cJD/emK 7LOTL9JZ/91o2rCg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 5F75B13297; Wed, 7 Aug 2024 21:14:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id jEDwFprjs2btYAAAD6G6ig (envelope-from ); Wed, 07 Aug 2024 21:14:02 +0000 Message-ID: <9d250713-d62d-459e-be3a-e6ad8da78d1a@suse.cz> Date: Wed, 7 Aug 2024 23:14:02 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/2] slub: Introduce CONFIG_SLUB_RCU_DEBUG Content-Language: en-US To: Jann Horn , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Marco Elver , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzbot+263726e59eab6b442723@syzkaller.appspotmail.com References: <20240802-kasan-tsbrcu-v6-0-60d86ea78416@google.com> <20240802-kasan-tsbrcu-v6-2-60d86ea78416@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.00 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; XM_UA_NO_VERSION(0.01)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FREEMAIL_TO(0.00)[google.com,gmail.com,arm.com,linux-foundation.org,linux.com,kernel.org,lge.com,linux.dev]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWELVE(0.00)[18]; MID_RHS_MATCH_FROM(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DWL_DNSWL_BLOCKED(0.00)[suse.cz:dkim]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[263726e59eab6b442723]; TO_DN_SOME(0.00)[] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -3.00 X-Rspamd-Queue-Id: 8563E21CFA On 8/2/24 22:31, Jann Horn wrote: > Currently, KASAN is unable to catch use-after-free in SLAB_TYPESAFE_BY_RCU > slabs because use-after-free is allowed within the RCU grace period by > design. > > Add a SLUB debugging feature which RCU-delays every individual > kmem_cache_free() before either actually freeing the object or handing it > off to KASAN, and change KASAN to poison freed objects as normal when this > option is enabled. > > For now I've configured Kconfig.debug to default-enable this feature in the > KASAN GENERIC and SW_TAGS modes; I'm not enabling it by default in HW_TAGS > mode because I'm not sure if it might have unwanted performance degradation > effects there. > > Note that this is mostly useful with KASAN in the quarantine-based GENERIC > mode; SLAB_TYPESAFE_BY_RCU slabs are basically always also slabs with a > ->ctor, and KASAN's assign_tag() currently has to assign fixed tags for > those, reducing the effectiveness of SW_TAGS/HW_TAGS mode. > (A possible future extension of this work would be to also let SLUB call > the ->ctor() on every allocation instead of only when the slab page is > allocated; then tag-based modes would be able to assign new tags on every > reallocation.) > > Tested-by: syzbot+263726e59eab6b442723@syzkaller.appspotmail.com > Signed-off-by: Jann Horn Acked-by: Vlastimil Babka [slab]