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Tue, 16 Jun 2020 09:10:36 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05G933ih037660; Tue, 16 Jun 2020 09:08:35 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 31p6s6w4s2-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Jun 2020 09:08:35 +0000 Received: from abhmp0019.oracle.com (abhmp0019.oracle.com [141.146.116.25]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 05G98O1L002227; Tue, 16 Jun 2020 09:08:25 GMT Received: from kadam (/41.57.98.10) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 16 Jun 2020 02:08:24 -0700 Date: Tue, 16 Jun 2020 12:08:07 +0300 From: Dan Carpenter To: Michal Hocko Subject: Re: [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree() Message-ID: <20200616090807.GK4151@kadam> References: <20200616015718.7812-1-longman@redhat.com> <20200616015718.7812-2-longman@redhat.com> <20200616064208.GA9499@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; 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Donenfeld" , Jarkko Sakkinen , virtualization@lists.linux-foundation.org, David Howells , linux-mm@kvack.org, linux-sctp@vger.kernel.org, keyrings@vger.kernel.org, kasan-dev@googlegroups.com, linux-stm32@st-md-mailman.stormreply.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-scsi@vger.kernel.org, James Morris , Matthew Wilcox , David Rientjes , Waiman Long , linux-pm@vger.kernel.org, ecryptfs@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, wireguard@lists.zx2c4.com, linux-fscrypt@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-amlogic@lists.infradead.org, Andrew Morton , linux-nfs@vger.kernel.org, Linus Torvalds , linux-wireless@vger.kernel.org, David Sterba , stable@vger.kernel.org, linux-kernel@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-security-module@vger.kernel.org, target-devel@vger.kernel.org, tipc-discussion@lists.sourceforge.net, linux-crypto@vger.kernel.org, Johannes Weiner , Joe Perches , linux-integrity@vger.kernel.org, linux-wpan@vger.kernel.org, netdev@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-ppp@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Jun 16, 2020 at 08:42:08AM +0200, Michal Hocko wrote: > On Mon 15-06-20 21:57:16, Waiman Long wrote: > > The kzfree() function is normally used to clear some sensitive > > information, like encryption keys, in the buffer before freeing it back > > to the pool. Memset() is currently used for the buffer clearing. However, > > it is entirely possible that the compiler may choose to optimize away the > > memory clearing especially if LTO is being used. To make sure that this > > optimization will not happen, memzero_explicit(), which is introduced > > in v3.18, is now used in kzfree() to do the clearing. > > > > Fixes: 3ef0e5ba4673 ("slab: introduce kzfree()") > > Cc: stable@vger.kernel.org > > Signed-off-by: Waiman Long > > Acked-by: Michal Hocko > > Although I am not really sure this is a stable material. Is there any > known instance where the memset was optimized out from kzfree? I told him to add the stable. Otherwise it will just get reported to me again. It's a just safer to backport it before we forget. regards, dan carpenter