From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Carpenter Subject: Re: [PATCH v4 1/3] mm/slab: Use memzero_explicit() in kzfree() Date: Tue, 16 Jun 2020 12:08:07 +0300 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; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20200616064208.GA9499-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+glpam-linux-mediatek=m.gmane-mx.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Michal Hocko Cc: "Jason A . Donenfeld" , Jarkko Sakkinen , virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, David Howells , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-sctp-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, keyrings-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kasan-dev-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, linux-stm32-XDFAJ8BFU24N7RejjzZ/Li2xQDfSxrLKVpNB7YpNyf8@public.gmane.org, devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, James Morris , Matthew Wilcox , David Rientjes , Waiman Long , linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ecryptfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, wireguard-/J5FBtcyxH5ZwnvJuMANYw@public.gmane.org, linux-fscrypt-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-amlogic-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Andrew Morton , linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linus Torvalds , linux-wir 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-u79uwXL29TY76Z2rM5mHXA@public.gmane.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