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| author | Nick Desaulniers <nick.desaulniers@gmail.com> | 2017-12-29 06:11:36 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-01-04 16:57:10 +0300 |
| commit | 29f1b2b0fecfae69e31833836f1da3136696eee5 (patch) | |
| tree | 4c299cbdc55a3cc3236e8ef3cc80e6af51ee4a57 /tools/testing/selftests/ptp | |
| parent | 00a5ae218d57741088068799b810416ac249a9ce (diff) | |
| download | linux-29f1b2b0fecfae69e31833836f1da3136696eee5.tar.xz | |
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 <tglx@linutronix.de>
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dimitri Sivanich <sivanich@hpe.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kselftest@vger.kernel.org
Cc: Shuah Khan <shuah@kernel.org>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Link: https://lkml.kernel.org/r/1514517100-18051-1-git-send-email-nick.desaulniers@gmail.com
Diffstat (limited to 'tools/testing/selftests/ptp')
| -rw-r--r-- | tools/testing/selftests/ptp/testptp.c | 4 |
1 files changed, 1 insertions, 3 deletions
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) |