From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1521880192; cv=none; d=google.com; s=arc-20160816; b=utKqtsk5gCfTyqdzuZX1xxqH0c5exTOf0SHmeZ/K4KO5nh4F6qYAi311mXmDocFSFx ups4ibO3AYqDIP4fvQszG6Rqspj9ugrpqoHRQnclAV5z9t/Nd3eq80snqgKcT9UauJcw 5aOZYdEJKPOAotvwoaZzC28Sn09GCnts5kDbiekvPImXAx2JaTpL9NbfKu6XzW46v2dm pJd3YoXWLUpPxB0SKzPsebvXmk1mAUk1qHa+DNJIXj48AIZJe42npB81e0id+cODS1ss u79c/v4Syxuinsi9bD+TTwZdy/vfCVKVgQFszkQErqSnONx7cbQTshxH/ep7INsFIuC5 Is0w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:sender:dkim-signature :arc-authentication-results; bh=7YUIQS8P3QkIZOHVpNJUPvT8NJaHk45qOwaIUm6aNe4=; b=sTPr3sbSO4YEmt62DmiM0kXOrPwJNbNdXgkZtGRx5SbhQIEsliwtZGEiw89a/qfHwc g0BaHVik3ZXupOeLF5Z0qlAb0KCQW7vjXhhdlhNvMGpqnHXBCClmTOcb80eAeWgbVzTB aaL1kWuPXx3HEMwsF3iwexRevT2bQZ9Ajxoe6/rw7iGY4WhNrSM3RmQ1KW1Dn88DPWjN Uy1NkF0yoIWULN4bAOCnG3oBiOeHjXsNlH7ZzLMwqSUrqFK0nFUVwuZCJTF7UWFae3yr FuOxnG5s5YvhtzmhEpgAnO4CGMgqeiSvpB2McK6L0rji2jKfJj2BmcQOI3yWW3mPXkIO IhgQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=BOKmvSRe; spf=pass (google.com: domain of mingo.kernel.org@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=mingo.kernel.org@gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=BOKmvSRe; spf=pass (google.com: domain of mingo.kernel.org@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=mingo.kernel.org@gmail.com X-Google-Smtp-Source: AG47ELtwqN6c3uVuKoE6BC56mRd9oawNBWOTko1tV5SXdzq/6ycvLSyvkyUX8v9OB9SoDIUuyPI+SQ== Sender: Ingo Molnar Date: Sat, 24 Mar 2018 09:29:47 +0100 From: Ingo Molnar To: Andrey Konovalov Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Jonathan Corbet , Catalin Marinas , Will Deacon , Christoffer Dall , Marc Zyngier , Christopher Li , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Masahiro Yamada , Michal Marek , Mark Rutland , Ard Biesheuvel , Yury Norov , Nick Desaulniers , Suzuki K Poulose , Kristina Martsenko , Punit Agrawal , Dave Martin , Michael Weiser , James Morse , Julien Thierry , Steve Capper , Tyler Baicar , "Eric W . Biederman" , Stephen Boyd , Thomas Gleixner , Paul Lawrence , Greg Kroah-Hartman , David Woodhouse , Sandipan Das , Kees Cook , Herbert Xu , Geert Uytterhoeven , Josh Poimboeuf , Arnd Bergmann , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-sparse@vger.kernel.org, linux-mm@kvack.org, linux-kbuild@vger.kernel.org, Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Kees Cook , Jann Horn , Mark Brand Subject: Re: [RFC PATCH v2 11/15] khwasan, mm: perform untagged pointers comparison in krealloc Message-ID: <20180324082947.3isostkpsjraefqt@gmail.com> References: <6eb08c160ae23eb890bd937ddf8346ba211df09f.1521828274.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6eb08c160ae23eb890bd937ddf8346ba211df09f.1521828274.git.andreyknvl@google.com> User-Agent: NeoMutt/20170609 (1.8.3) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595752716297382191?= X-GMAIL-MSGID: =?utf-8?q?1595807044663980395?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: * Andrey Konovalov wrote: > The krealloc function checks where the same buffer was reused or a new one > allocated by comparing kernel pointers. KHWASAN changes memory tag on the > krealloc'ed chunk of memory and therefore also changes the pointer tag of > the returned pointer. Therefore we need to perform comparison on untagged > (with tags reset) pointers to check whether it's the same memory region or > not. > > Signed-off-by: Andrey Konovalov > --- > mm/slab_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index a33e61315ca6..5911f2194cf7 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1494,7 +1494,7 @@ void *krealloc(const void *p, size_t new_size, gfp_t flags) > } > > ret = __do_krealloc(p, new_size, flags); > - if (ret && p != ret) > + if (ret && khwasan_reset_tag(p) != khwasan_reset_tag(ret)) > kfree(p); Small nit: If 'reset' here means an all zeroes tag (upper byte) then khwasan_clear_tag() might be a slightly easier to read primitive? Thanks, Ingo