From 29f1b2b0fecfae69e31833836f1da3136696eee5 Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Thu, 28 Dec 2017 22:11:36 -0500 Subject: posix-timers: Prevent UB from shifting negative signed value Shifting a negative signed number is undefined behavior. Looking at the macros MAKE_PROCESS_CPUCLOCK and FD_TO_CLOCKID, it seems that the subexpression: (~(clockid_t) (pid) << 3) where clockid_t resolves to a signed int, which once negated, is undefined behavior to shift the value of if the results thus far are negative. It was further suggested to make these macros into inline functions. Suggested-by: Thomas Gleixner Signed-off-by: Nick Desaulniers Signed-off-by: Thomas Gleixner Cc: Dimitri Sivanich Cc: Frederic Weisbecker Cc: Al Viro Cc: linux-kselftest@vger.kernel.org Cc: Shuah Khan Cc: Deepa Dinamani Link: https://lkml.kernel.org/r/1514517100-18051-1-git-send-email-nick.desaulniers@gmail.com --- tools/testing/selftests/ptp/testptp.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'tools/testing/selftests/ptp') diff --git a/tools/testing/selftests/ptp/testptp.c b/tools/testing/selftests/ptp/testptp.c index 5d2eae16f7ee..a5d8f0ab0da0 100644 --- a/tools/testing/selftests/ptp/testptp.c +++ b/tools/testing/selftests/ptp/testptp.c @@ -60,9 +60,7 @@ static int clock_adjtime(clockid_t id, struct timex *tx) static clockid_t get_clockid(int fd) { #define CLOCKFD 3 -#define FD_TO_CLOCKID(fd) ((~(clockid_t) (fd) << 3) | CLOCKFD) - - return FD_TO_CLOCKID(fd); + return (((unsigned int) ~fd) << 3) | CLOCKFD; } static void handle_alarm(int s) -- cgit v1.2.3-59-g8ed1b