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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678816586; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=gd+1sCvHMwOBO08sAoxbEvUITd9t9ya85GRQ8ebYZaE=; b=Rx5I1ZFamPORLL1URj6Lvqj63fsj5EGDQOPhW6ZFxQrsJNo9w/SOLVlZhvmfKzygQa YYpT10YOUlJI9FZBi1LA2QIT64dyfisfjSSFIzo6806c15E/lpIKoAeTP8H/rSGrHOEX hdU9dOgZskf8/UAysA+5q2yi9852ab+vZl0nRTa/jKp/SLmnJTizhzLsl0d3ueNcNu6L Dwt2i9TLecRDjCoGZohK/U90Slck7Zivziv6Trbfz4zLy6PRo8xb99si5d9V/iL/Foj7 CokJq+VhA/SZH0I7LcCMF/nGV4+cKLEYh/Sf3hXmCgzs1auKyQgH/gcblmJ89LErMNI4 vzGg== X-Gm-Message-State: AO0yUKXyJyCS6AsiRQN+H2HO2OMYs8hSWIKwqLe5vJNBKuyknp5+8jEf 0tQLVVF7ruRR7C3YgQd8WqwpE/en1dmeXMS6Ec8= X-Google-Smtp-Source: AK7set+5qOEOnZpGZ6M48MgZ7XIb5WwECpEEcWyAPVDVDBcK7f5d2ZsuhIZXAaXLi5ZEVybY+17PYqY4imu75SgdEe8= X-Received: by 2002:a62:1d57:0:b0:623:c7ff:46d8 with SMTP id d84-20020a621d57000000b00623c7ff46d8mr2948536pfd.6.1678816586037; Tue, 14 Mar 2023 10:56:26 -0700 (PDT) MIME-Version: 1.0 References: <59f433e00f7fa985e8bf9f7caf78574db16b67ab.1678491668.git.andreyknvl@google.com> In-Reply-To: From: Andrey Konovalov Date: Tue, 14 Mar 2023 18:56:15 +0100 Message-ID: Subject: Re: [PATCH 5/5] kasan: suppress recursive reports for HW_TAGS To: Marco Elver Cc: andrey.konovalov@linux.dev, Catalin Marinas , Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , kasan-dev@googlegroups.com, Vincenzo Frascino , Will Deacon , linux-arm-kernel@lists.infradead.org, Peter Collingbourne , Evgenii Stepanov , Andrew Morton , linux-mm@kvack.org, Weizhao Ouyang , linux-kernel@vger.kernel.org, Andrey Konovalov Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6253440022 X-Stat-Signature: e4m5jf15af6kmnbpqxymdafercm6h4w8 X-Rspam-User: X-HE-Tag: 1678816587-858760 X-HE-Meta: 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 FIPnw8Hp 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 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 Mon, Mar 13, 2023 at 12:20=E2=80=AFPM Marco Elver wro= te: > > > + * Hardware Tag-Based KASAN instead relies on: > > + * For #1: Resetting tags via kasan_reset_tag(). > > + * For #2: Supression of tag checks via CPU, see report_suppress_start= /end(). > > Typo: "Suppression" Will fix in v2. > > +static void report_suppress_start(void) > > +{ > > +#ifdef CONFIG_KASAN_HW_TAGS > > + /* > > + * Disable migration for the duration of printing a KASAN repor= t, as > > + * hw_suppress_tag_checks_start() disables checks on the curren= t CPU. > > + */ > > + migrate_disable(); > > This still allows this task to be preempted by another task. If the > other task is scheduled in right after hw_suppress_tag_checks_start() > then there won't be any tag checking in that task. If HW-tags KASAN is > used as a mitigation technique, that may unnecessarily weaken KASAN, > because right after report_suppress_start(), it does > spin_lock_irqsave() which disables interrupts (and thereby preemption) > anyway. > > Why not just use preempt_disable()? Ah, yes, I intended to do that but forgot to make the change. I'll wait for comments from arm64 maintainers on the other patches and then send v2 with a fix. Thank you, Marco!