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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id b15sm8864879pfd.139.2020.04.25.15.48.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 25 Apr 2020 15:48:32 -0700 (PDT) Date: Sat, 25 Apr 2020 15:48:31 -0700 From: Kees Cook To: Changbin Du Cc: Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/slub: do not place freelist pointer to middle of object if redzone is on Message-ID: <202004251547.0F8E6856B@keescook> References: <20200425091338.24283-1-changbin.du@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200425091338.24283-1-changbin.du@gmail.com> 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 Sat, Apr 25, 2020 at 05:13:38PM +0800, Changbin Du wrote: > The recent kernel fails to boot when slub redzone is turned on. This is > caused by commit 3202fa62fb ("slub: relocate freelist pointer to middle of > object") which relocates freelist pointer to middle of object. In this > case, get_track() gets a wrong address and then the redzone is overwritten. Hi! A fix for this is already in -next: https://www.ozlabs.org/~akpm/mmotm/broken-out/slub-avoid-redzone-when-choosing-freepointer-location.patch the above doesn't disable the mitigation when using redzones, so I prefer that to this suggested solution. -- Kees Cook