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[217.140.101.70]) by mx.google.com with ESMTP id y2si180967ejw.302.2019.02.27.09.21.18 for ; Wed, 27 Feb 2019 09:21:18 -0800 (PST) Received-SPF: pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of catalin.marinas@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5A1D31688; Wed, 27 Feb 2019 09:21:17 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4B0543F703; Wed, 27 Feb 2019 09:21:16 -0800 (PST) Date: Wed, 27 Feb 2019 17:21:13 +0000 From: Catalin Marinas To: Qian Cai Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page_ext: fix an imbalance with kmemleak Message-ID: <20190227172113.GE125513@arrakis.emea.arm.com> References: <20190227171556.75444-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190227171556.75444-1-cai@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed, Feb 27, 2019 at 12:15:56PM -0500, Qian Cai wrote: > After offlined a memory block, kmemleak scan will trigger a crash, as it > encounters a page ext address that has already been freed during memory > offlining. At the beginning in alloc_page_ext(), it calls > kmemleak_alloc(), but it does not call kmemleak_free() in > __free_page_ext(). [...] > diff --git a/mm/page_ext.c b/mm/page_ext.c > index 8c78b8d45117..b68f2a58ea3b 100644 > --- a/mm/page_ext.c > +++ b/mm/page_ext.c > @@ -288,6 +288,7 @@ static void __free_page_ext(unsigned long pfn) > base = get_entry(ms->page_ext, pfn); > free_page_ext(base); > ms->page_ext = NULL; > + kmemleak_free(base); > } The kmemleak_free() call should be placed before free_page_ext() to avoid a small window where the address has been freed but kmemleak not informed. -- Catalin