From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E5EFBC433DF for ; Thu, 14 May 2020 12:08:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 66C86206A5 for ; Thu, 14 May 2020 12:08:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 66C86206A5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=perches.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D5501900145; Thu, 14 May 2020 08:08:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CDE048E0005; Thu, 14 May 2020 08:08:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BA57F900145; Thu, 14 May 2020 08:08:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0005.hostedemail.com [216.40.44.5]) by kanga.kvack.org (Postfix) with ESMTP id A17748E0005 for ; Thu, 14 May 2020 08:08:56 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 466F7180AD811 for ; Thu, 14 May 2020 12:08:56 +0000 (UTC) X-FDA: 76815203472.15.humor31_13ca1dbed6b20 X-HE-Tag: humor31_13ca1dbed6b20 X-Filterd-Recvd-Size: 3197 Received: from smtprelay.hostedemail.com (smtprelay0144.hostedemail.com [216.40.44.144]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 14 May 2020 12:08:55 +0000 (UTC) Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay06.hostedemail.com (Postfix) with ESMTP id 99D5A18224D7E; Thu, 14 May 2020 12:08:55 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: taste99_13733fd571143 X-Filterd-Recvd-Size: 2031 Received: from XPS-9350.home (unknown [47.151.136.130]) (Authenticated sender: joe@perches.com) by omf16.hostedemail.com (Postfix) with ESMTPA; Thu, 14 May 2020 12:08:53 +0000 (UTC) Message-ID: Subject: Re: [PATCH v3] mm: Add kvfree_sensitive() for freeing sensitive data objects From: Joe Perches To: Matthew Wilcox , Balbir Singh Cc: Waiman Long , Andrew Morton , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , linux-mm@kvack.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , David Rientjes Date: Thu, 14 May 2020 05:08:52 -0700 In-Reply-To: <20200514120018.GA16070@bombadil.infradead.org> References: <20200407200318.11711-1-longman@redhat.com> <1158ff38-c65d-379f-8ae7-6f507d9fc8dd@gmail.com> <20200514120018.GA16070@bombadil.infradead.org> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.1-2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit 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 Thu, 2020-05-14 at 05:00 -0700, Matthew Wilcox wrote: > On Thu, May 14, 2020 at 09:00:40PM +1000, Balbir Singh wrote: > > I wonder if the right thing to do is also to disable pre-emption, just so that the thread does not linger on with sensitive data. > > > > void kvfree_sensitive(const void *addr, size_t len) > > { > > preempt_disable(); > > if (likely(!ZERO_OR_NULL_PTR(addr))) { > > memzero_explicit((void *)addr, len); > > kvfree(addr); > > } > > preempt_enable(); > > } > > EXPORT_SYMBOL(kvfree_sensitive); > > If it's _that_ sensitive then the caller should have disabled preemption. > Because preemption could otherwise have occurred immediately before > kvfree_sensitive() was called. static inline ?