From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Date: Tue, 16 Jun 2020 19:43:16 +0000 Subject: Re: [PATCH v4 0/3] mm, treewide: Rename kzfree() to kfree_sensitive() Message-Id: <5c70746c-ecfc-316f-f1ff-ab432cf9f32d@redhat.com> List-Id: References: <20200616015718.7812-1-longman@redhat.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Joe Perches , Andrew Morton , David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Linus Torvalds , Matthew Wilcox , David Rientjes Cc: "Jason A . Donenfeld" , Michal Hocko , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-sctp@vger.kernel.org, target-devel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-scsi@vger.kernel.org, kasan-dev@googlegroups.com, linux-wpan@vger.kernel.org, Dan Carpenter , linux-pm@vger.kernel.org, ecryptfs@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-amlogic@lists.infradead.org, virtualization@lists.linux-foundation.org, linux-nfs@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, David Sterba , linux-bluetooth@vger.kernel.org, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, tipc-discussion@lists.sourceforge.net, linux-crypto@vger.kernel.org, Johannes Weiner , linux-integrity@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, wireguard@lists.zx2c4.com, linux-ppp@vger.kernel.org On 6/16/20 2:53 PM, Joe Perches wrote: > On Mon, 2020-06-15 at 21:57 -0400, Waiman Long wrote: >> v4: >> - Break out the memzero_explicit() change as suggested by Dan Carpenter >> so that it can be backported to stable. >> - Drop the "crypto: Remove unnecessary memzero_explicit()" patch for >> now as there can be a bit more discussion on what is best. It will be >> introduced as a separate patch later on after this one is merged. > To this larger audience and last week without reply: > https://lore.kernel.org/lkml/573b3fbd5927c643920e1364230c296b23e7584d.camel@perches.com/ > > Are there _any_ fastpath uses of kfree or vfree? I am not sure about that, but both of them can be slow. > > Many patches have been posted recently to fix mispairings > of specific types of alloc and free functions. > > To eliminate these mispairings at a runtime cost of four > comparisons, should the kfree/vfree/kvfree/kfree_const > functions be consolidated into a single kfree? > > Something like the below: > > void kfree(const void *addr) > { > if (is_kernel_rodata((unsigned long)addr)) > return; > > if (is_vmalloc_addr(addr)) > _vfree(addr); > else > _kfree(addr); > } > is_kernel_rodata() is inlined, but is_vmalloc_addr() isn't. So the overhead can be a bit bigger. Cheers, Longman