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Fri, 20 Dec 2019 10:51:56 -0800 (PST) Date: Fri, 20 Dec 2019 19:49:49 +0100 In-Reply-To: <20191220184955.223741-1-glider@google.com> Message-Id: <20191220184955.223741-37-glider@google.com> Mime-Version: 1.0 References: <20191220184955.223741-1-glider@google.com> X-Mailer: git-send-email 2.24.1.735.g03f4e72817-goog Subject: [PATCH RFC v4 36/42] kmsan: disable strscpy() optimization under KMSAN From: glider@google.com To: Vegard Nossum , Dmitry Vyukov , Marco Elver , Andrey Konovalov , linux-mm@kvack.org Cc: glider@google.com, viro@zeniv.linux.org.uk, adilger.kernel@dilger.ca, akpm@linux-foundation.org, aryabinin@virtuozzo.com, luto@kernel.org, ard.biesheuvel@linaro.org, arnd@arndb.de, hch@infradead.org, hch@lst.de, darrick.wong@oracle.com, davem@davemloft.net, dmitry.torokhov@gmail.com, ebiggers@google.com, edumazet@google.com, ericvh@gmail.com, gregkh@linuxfoundation.org, harry.wentland@amd.com, herbert@gondor.apana.org.au, iii@linux.ibm.com, mingo@elte.hu, jasowang@redhat.com, axboe@kernel.dk, m.szyprowski@samsung.com, mark.rutland@arm.com, martin.petersen@oracle.com, schwidefsky@de.ibm.com, willy@infradead.org, mst@redhat.com, mhocko@suse.com, monstr@monstr.eu, pmladek@suse.com, cai@lca.pw, rdunlap@infradead.org, robin.murphy@arm.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, tiwai@suse.com, tytso@mit.edu, tglx@linutronix.de, gor@linux.ibm.com, wsa@the-dreams.de Content-Type: text/plain; charset="UTF-8" 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: Disable the efficient 8-byte reading under KMSAN to avoid false positives. Signed-off-by: Alexander Potapenko To: Alexander Potapenko Cc: Vegard Nossum Cc: Dmitry Vyukov Cc: Marco Elver Cc: Andrey Konovalov Cc: linux-mm@kvack.org --- v4: - actually disable the optimization under KMSAN via max=0 - use IS_ENABLED as requested by Marco Elver Change-Id: I25d1acf5c3df6eff85894cd94f5ddbe93308271c --- lib/string.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/lib/string.c b/lib/string.c index 08ec58cc673b..8f7fb0617240 100644 --- a/lib/string.c +++ b/lib/string.c @@ -202,6 +202,14 @@ ssize_t strscpy(char *dest, const char *src, size_t count) max = 0; #endif + /* + * read_word_at_a_time() below may read uninitialized bytes after the + * trailing zero and use them in comparisons. Disable this optimization + * under KMSAN to prevent false positive reports. + */ + if (IS_ENABLED(CONFIG_KMSAN)) + max = 0; + while (max >= sizeof(unsigned long)) { unsigned long c, data; -- 2.24.1.735.g03f4e72817-goog