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AJvYcCVvS+AupPWImxNzGUnOYRWU4BNE/AYxpptdeFAQIzPypFIfYopvBzZy1R30dB4z90K+jL7k8g5M3+77OsnJvmYHgw8= X-Gm-Message-State: AOJu0Yw1hg+gmygrbD5vHu+KxDuV/GfRzs/kC4GKgeWYFtbKC9DJIi6m SWbREIl8dWh6pXqakh3ajj9R7jBE+L3iz94YsGiKiIOS78uqP51EnHC3B+i+r8fPiXjlamspcrM PCwO4exKZrEyCtyLfF7KbTk+tQsLNKQhYiLp4 X-Google-Smtp-Source: AGHT+IHeLfopYA5+BXjlrv9nKiZRDnXJoaZQyRkMEillXRUwh8YU4XiIl4Kkmp/3gkn2YGckbTHD0I0KZoIHNmRKHnE= X-Received: by 2002:a05:6402:13d0:b0:5bd:3fff:7196 with SMTP id 4fb4d7f45d1cf-5bd476d59e2mr100042a12.6.1723559744140; Tue, 13 Aug 2024 07:35:44 -0700 (PDT) MIME-Version: 1.0 References: <20240809-kasan-tsbrcu-v8-0-aef4593f9532@google.com> <20240809-kasan-tsbrcu-v8-2-aef4593f9532@google.com> In-Reply-To: From: Jann Horn Date: Tue, 13 Aug 2024 16:35:07 +0200 Message-ID: Subject: Re: [PATCH v8 2/2] slub: Introduce CONFIG_SLUB_RCU_DEBUG To: Shinichiro Kawasaki Cc: Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Marco Elver , "kasan-dev@googlegroups.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , David Sterba , "syzbot+263726e59eab6b442723@syzkaller.appspotmail.com" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 890221C003C X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xutkxgqn4newamjc3aenud4rjcfmzurd X-HE-Tag: 1723559746-943273 X-HE-Meta: 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 AqjUceJ1 PTAh6sm6SoAUkfeqZdwFkFaeEzS3HnvrVxTQnMY7w63ODJYscqqxuawmw8X3VVlc9KiHqOUgFk3l7gOiKQw5zcz+y4bz/bhabgwoRxOmVc5R39Gq7Thne2P/1kJNFaBGfxLL1ijUIrOA3BM+nbGkkn/dujr/ADJKObM87lWc4c03Dl9/hUUMVCbhOIpFVtzk7zbaVzI39mhwHB4U/EuJmVu62wOmWigTf1KbkTqDAVZ1ny/+qHYcEbVJlGhACSUwvdUShSNkAFqSW7k+1YKELwWlMFAHg+iWccbx0Iw1nidNqqCHfXtvDhTYQ2pmyehYZsgZOx6jAQ12Zy74Q6XPeTtb5Huna6cDb6Y/5LHiCQWcMjsFEJfpbHBhsoKDxKpHJNAQfAWWCxK74+J9FU3shRrb+oIHYxP6csA10uzXtY+XE5CUHJkRGSiZNAMVMFTchUkTIW9IR5wBggTqxjPY9NsL5uxF3J5zcvhmw 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: List-Subscribe: List-Unsubscribe: Hi! On Tue, Aug 13, 2024 at 11:03=E2=80=AFAM Shinichiro Kawasaki wrote: > Hello Jann, let me ask a question about this patch. When I tested the > next-20240808 kernel which includes this patch, I observed that > slab_free_after_rcu_debug() reports many WARNs. Please find my question i= n line. Thanks for testing linux-next. > On Aug 09, 2024 / 17:36, Jann Horn wrote: [...] > > +#ifdef CONFIG_SLUB_RCU_DEBUG > > +static void slab_free_after_rcu_debug(struct rcu_head *rcu_head) > > +{ > > + struct rcu_delayed_free *delayed_free =3D > > + container_of(rcu_head, struct rcu_delayed_free, h= ead); > > + void *object =3D delayed_free->object; > > + struct slab *slab =3D virt_to_slab(object); > > + struct kmem_cache *s; > > + > > + kfree(delayed_free); > > + > > + if (WARN_ON(is_kfence_address(object))) > > + return; > > With the kernel configs above, I see the many WARNs are reported here. > When SLUB_RCU_DEBUG is enabled, should I disable KFENCE? These features are supposed to be compatible. In the version you tested (https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next-history.gi= t/tree/mm/slub.c?h=3Dnext-20240808#n4550), I made a mistake and wrote "if (WARN_ON(is_kfence_address(rcu_head)))" instead of "if (WARN_ON(is_kfence_address(object)))". That issue was fixed in v6 of the series after syzbot and the Intel test bot ran into the same issue.