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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id e1sm12311920pgu.17.2022.01.24.10.24.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jan 2022 10:24:34 -0800 (PST) Date: Mon, 24 Jan 2022 10:24:34 -0800 From: Kees Cook To: Marco Elver Cc: Andrew Morton , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Brendan Higgins , linux-hardening@vger.kernel.org, Nico Pache Subject: Re: [PATCH] kasan: test: fix compatibility with FORTIFY_SOURCE Message-ID: <202201241024.DA581869@keescook> References: <20220124160744.1244685-1-elver@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220124160744.1244685-1-elver@google.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 673ED100008 X-Stat-Signature: ru58pdafg74tjw458fkkn88jdjung3f5 Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=alUnBjwA; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf05.hostedemail.com: domain of keescook@chromium.org designates 209.85.222.50 as permitted sender) smtp.mailfrom=keescook@chromium.org X-HE-Tag: 1643050102-134932 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 Mon, Jan 24, 2022 at 05:07:44PM +0100, Marco Elver wrote: > With CONFIG_FORTIFY_SOURCE enabled, string functions will also perform > dynamic checks using __builtin_object_size(ptr), which when failed will > panic the kernel. > > Because the KASAN test deliberately performs out-of-bounds operations, > the kernel panics with FORITY_SOURCE, for example: > > | kernel BUG at lib/string_helpers.c:910! > | invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI > | CPU: 1 PID: 137 Comm: kunit_try_catch Tainted: G B 5.16.0-rc3+ #3 > | Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 > | RIP: 0010:fortify_panic+0x19/0x1b > | ... > | Call Trace: > | > | kmalloc_oob_in_memset.cold+0x16/0x16 > | ... > > Fix it by also hiding `ptr` from the optimizer, which will ensure that > __builtin_object_size() does not return a valid size, preventing > fortified string functions from panicking. > > Reported-by: Nico Pache > Signed-off-by: Marco Elver Yup, more good fixes. Thanks! Reviewed-by: Kees Cook -- Kees Cook