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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id v8sm2900365pjk.39.2020.12.09.10.54.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Dec 2020 10:54:40 -0800 (PST) Date: Wed, 9 Dec 2020 10:54:39 -0800 From: Kees Cook To: Dmitry Vyukov Cc: akpm@linux-foundation.org, andreyknvl@google.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Stephen Rothwell , Marco Elver Subject: Re: [PATCH] kcov: don't instrument with UBSAN Message-ID: <202012091054.08D70D4F@keescook> References: <20201209100152.2492072-1-dvyukov@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201209100152.2492072-1-dvyukov@google.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 Wed, Dec 09, 2020 at 11:01:52AM +0100, Dmitry Vyukov wrote: > Both KCOV and UBSAN use compiler instrumentation. If UBSAN detects a bug > in KCOV, it may cause infinite recursion via printk and other common > functions. We already don't instrument KCOV with KASAN/KCSAN for this > reason, don't instrument it with UBSAN as well. > > As a side effect this also resolves the following gcc warning: > > conflicting types for built-in function '__sanitizer_cov_trace_switch'; > expected 'void(long unsigned int, void *)' [-Wbuiltin-declaration-mismatch] > > It's only reported when kcov.c is compiled with any of the sanitizers > enabled. Size of the arguments is correct, it's just that gcc uses 'long' > on 64-bit arches and 'long long' on 32-bit arches, while kernel type is > always 'long long'. > > Reported-by: Stephen Rothwell > Suggested-by: Marco Elver > Signed-off-by: Dmitry Vyukov Reviewed-by: Kees Cook Thanks for chasing this down! Andrew, can you add this to the stack of ubsan patches you're carrying, please? -- Kees Cook