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b=e/VzJZYoLKtf+M1/ZFVlJVERgZhOI5sX9iBIKBC19rg5IpwfmNoYHDWxwHFThqoBK u1mMlajcwQx4PH7oOBGSGWPxJ/cA25CuGB8DNvgJ0WRUIrs6CN8k9uXboWPjW3Etbq iwD8gqCU8jMVvqJsbFz3+xoUYScVnJ/l6mQ+u47jD9o/64WdZvWmJ+hH4hZvw43VdC 3esxSCJplc7cVi93uM0qo1Aa1Z9PvEPm+FCVzi5IH3HZbevIRWBLV1hsa44m4T3+qx nPy2bAJtJDry0sbjsks/GARUeVYYfXgxDbVYdH1DJhUOvUkbgQMFB6RhxFuIZhiwY+ d2b9QyO+2nO9w== Date: Tue, 25 Mar 2025 12:45:10 -0700 From: Kees Cook To: "Christoph Lameter (Ampere)" Cc: Vlastimil Babka , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Miguel Ojeda , Nathan Chancellor , Marco Elver , Nick Desaulniers , Przemek Kitszel , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 5/5] [DEBUG] slab: Report number of NULLings Message-ID: <202503251244.CA3E0F8@keescook> References: <20250321202620.work.175-kees@kernel.org> <20250321204105.1898507-5-kees@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: C482D180008 X-Stat-Signature: tuejk64h83rzhbhfkz46p3ej5gkg1gxa X-Rspam-User: X-HE-Tag: 1742931914-977962 X-HE-Meta: U2FsdGVkX1+KSsqKJyhtmifktifCmOiX4mQZ1uQNU31Me4KjXkvS51XNaSyVxrtegmD0nREtyVzdO5rif7J82KUbIcKHIb515tHU1K5+OXatKvLGajVwjWjIU9/2yS4SBc0T1jdCZhLE92gq1MLaaKJefcitkm7O8SoGM6Y0giJR+iEt62quSoWWeZBCq3gDHTFzpWoAguWNex2nzC98egjj36GSXHvw3sE4OfF1Cus7sfBL8wZOlJ4kuetbyiOS9penr2fGN2vq/BAqMQtWyz3cCeV02zrcBZ/gQ0CksR6Qs78bcbL8wilwpp3L1IumJgHvHOGtWeZoVjtYX2CoYaJKFtMVh3fp1Dc8UwDOvXgMEshymRAdMTcHLNX88t2Grtknex68t8LYm4zZwjapcwn4O8Au33SP1t1csOopa7u3M/Q2neg451wpiZ390MxGG0f3KI0KAmdlgpk/+B0Cf4bv5RlOTwaaL1nuOFMfR+ebwlJBcbjBL+UW6SzIMyMvwjRqwPzW6feCP+6gkImRsTVuQpnmA1n2pF30YD3ZceIxdUx541lcuCW0cG+1WfpEvLKqv8BjFGYIAQlKbsVFaAQxZMgNm5bwoCpaaPerM7mqIOdK+HUG+GL+A8FfxH8AGhbsb9GpuqW4GodEVgEokBTQ9zAapOajS+AdPS+9GNQ5kYO1cEtZkHmBhjFJ1mugZQ2G/vjYyMpZDxbbTOguKEPikbq5onWZjU+yl7PBxfKb+g3zIub9yNOgwBHeNiici68w5Tt6OTpl75XD67WIi7XuQSqr7zD060SPen98zv0ZJ+CsGURfNCYBQreX7uLFkyzrDoi+5hVAhwH+xl5ty+CLSh07XE+xBBCTWoc+zkew+6gpR6bM7DZ8XC7Ur/FaGX/wJxht/yHL/glRoIKdK7HzkF2F21zjU8kiDdn4cVwaAT7Xd1y7nu+eq7Qo/zb6VflnqIqzsHevmpfQFXm zm4YrbNG FnnVR97sCTQR47/y+YAASUSbCeXRNlHUlsQGoQS4rFQLOWMgNZ0tnyaRqJqOD4KEoblIzDss/2adJRNpDJLvGIKq/9jramaQTtwWx/Wbgfu81jF4f6zRkSjXQ/Qca3TxIXgsUUHMr4b1O+4osoYf+ugw81K3F3AUr4lB7Kc1GcxpnyKApN342g5ugB2JY6Ol6sBszHCWoI/18yGcDQberli+xaz+K3V06xYyR9Xmr9Hh02KJqHqyS/RGaXs7e3v55AmZIF7Tl28vPvF8HNCp+/ZKpqu/8FOCrUcYvPVp3gFhb+LiUKLU3gW6BVzD9MbTQvrBXIG11BvEoxNY= 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: List-Subscribe: List-Unsubscribe: On Mon, Mar 24, 2025 at 09:16:47AM -0700, Christoph Lameter (Ampere) wrote: > On Fri, 21 Mar 2025, Kees Cook wrote: > > > diff --git a/include/linux/slab.h b/include/linux/slab.h > > index 2717ad238fa2..a4740c8b6ccb 100644 > > --- a/include/linux/slab.h > > +++ b/include/linux/slab.h > > @@ -469,6 +469,8 @@ void __kfree(const void *objp); > > void __kfree_sensitive(const void *objp); > > size_t __ksize(const void *objp); > > > > +extern atomic_t count_nulled; > > That is a scalability issue. Use a vmstat counter instead? Yeah, this patch (marked "DEBUG") isn't intended for upstreaming. It was just a quick hack to get a ballpark statistic. :) -- Kees Cook