The timespec_sub function, as implemented in several timer
selftests, is prone to integer overflow on 32-bit systems.
The calculation `NSEC_PER_SEC * b.tv_sec` is performed using
32-bit arithmetic, and the result overflows before being
stored in the 64-bit `ret` variable. This leads to incorrect
time delta calculations and test failures.
As suggested by tglx, this patch fixes the issue by:
1. Creating a new `static inline` helper function,
`timespec_to_ns`, which safely converts a `timespec` to
nanoseconds by casting `tv_sec` to `long long` before
multiplying with `NSEC_PER_SEC`.
2. Placing the new helper and a rewritten `timespec_sub` into
a common header: tools/testing/selftests/timers/helpers.h.
3. Removing the duplicated, buggy implementations from all
timer selftests and replacing them with an #include of the
new header.
This consolidates the code and ensures the calculation is
correctly performed using 64-bit arithmetic across all tests.
Changes in v2:
- Per tglx's feedback, instead of changing NSEC_PER_SEC globally,
this version consolidates the buggy timespec_sub() implementations
into a new 32-bit safe inline function in a shared header.
- Amended the commit message to be more descriptive.
---
.../selftests/timers/alarmtimer-suspend.c | 15 +++------
tools/testing/selftests/timers/helpers.h | 31 +++++++++++++++++++
tools/testing/selftests/timers/nanosleep.c | 2 +-
tools/testing/selftests/timers/nsleep-lat.c | 12 ++-----
.../testing/selftests/timers/valid-adjtimex.c | 8 ++---
5 files changed, 43 insertions(+), 25 deletions(-)
create mode 100644 tools/testing/selftests/timers/helpers.h
diff --git a/tools/testing/selftests/timers/alarmtimer-suspend.c
b/tools/testing/selftests/timers/alarmtimer-suspend.c
index a9ef76ea6051..e85ab182abe5 100644
--- a/tools/testing/selftests/timers/alarmtimer-suspend.c
+++ b/tools/testing/selftests/timers/alarmtimer-suspend.c
@@ -31,8 +31,9 @@
#include <include/vdso/time64.h>
#include <errno.h>
#include "../kselftest.h"
+#include "helpers.h"
-#define UNREASONABLE_LAT (NSEC_PER_SEC * 5) /* hopefully we resume in 5 secs */
+#define UNREASONABLE_LAT (NSEC_PER_SEC * 5LL) /* hopefully we resume in 5 secs
*/
#define SUSPEND_SECS 15
int alarmcount;
@@ -70,14 +71,6 @@ char *clockstring(int clockid)
}
-long long timespec_sub(struct timespec a, struct timespec b)
-{
- long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
-
- ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
- return ret;
-}
-
int final_ret;
void sigalarm(int signo)
@@ -88,8 +81,8 @@ void sigalarm(int signo)
clock_gettime(alarm_clock_id, &ts);
alarmcount++;
- delta_ns = timespec_sub(start_time, ts);
- delta_ns -= NSEC_PER_SEC * SUSPEND_SECS * alarmcount;
+ delta_ns = timespec_sub(ts, start_time);
+ delta_ns -= (long long)NSEC_PER_SEC * SUSPEND_SECS * alarmcount;
printf("ALARM(%i): %ld:%ld latency: %lld ns ", alarmcount, ts.tv_sec,
ts.tv_nsec, delta_ns);
diff --git a/tools/testing/selftests/timers/helpers.h
b/tools/testing/selftests/timers/helpers.h
new file mode 100644
index 000000000000..652f20247091
--- /dev/null
+++ b/tools/testing/selftests/timers/helpers.h
@@ -0,0 +1,31 @@
+#ifndef SELFTESTS_TIMERS_HELPERS_H
+#define SELFTESTS_TIMERS_HELPERS_H
+
+#include <time.h>
+
+#ifndef NSEC_PER_SEC
+#define NSEC_PER_SEC 1000000000L
+#endif
+
+/*
+ * timespec_to_ns - Convert timespec to nanoseconds
+ */
+static inline long long timespec_to_ns(const struct timespec *ts)
+{
+ return ((long long) ts->tv_sec * NSEC_PER_SEC) + ts->tv_nsec;
+}
+
+/*
+ * timespec_sub - Subtract two timespec values
+ *
+ * @a: first timespec
+ * @b: second timespec
+ *
+ * Returns a - b in nanoseconds.
+ */
+static inline long long timespec_sub(struct timespec a, struct timespec b)
+{
+ return timespec_to_ns(&a) - timespec_to_ns(&b);
+}
+
+#endif /* SELFTESTS_TIMERS_HELPERS_H */
diff --git a/tools/testing/selftests/timers/nanosleep.c
b/tools/testing/selftests/timers/nanosleep.c
index 252c6308c569..41c33629d5f0 100644
--- a/tools/testing/selftests/timers/nanosleep.c
+++ b/tools/testing/selftests/timers/nanosleep.c
@@ -138,7 +138,7 @@ int main(int argc, char **argv)
fflush(stdout);
length = 10;
- while (length <= (NSEC_PER_SEC * 10)) {
+ while (length <= (NSEC_PER_SEC * 10LL)) {
ret = nanosleep_test(clockid, length);
if (ret == UNSUPPORTED) {
ksft_test_result_skip("%-31s\n",
clockstring(clockid));
diff --git a/tools/testing/selftests/timers/nsleep-lat.c
b/tools/testing/selftests/timers/nsleep-lat.c
index de23dc0c9f97..c888a77aab7a 100644
--- a/tools/testing/selftests/timers/nsleep-lat.c
+++ b/tools/testing/selftests/timers/nsleep-lat.c
@@ -26,6 +26,7 @@
#include <signal.h>
#include <include/vdso/time64.h>
#include "../kselftest.h"
+#include "helpers.h"
#define UNRESONABLE_LATENCY 40000000 /* 40ms in nanosecs */
@@ -74,14 +75,6 @@ struct timespec timespec_add(struct timespec ts, unsigned
long long ns)
}
-long long timespec_sub(struct timespec a, struct timespec b)
-{
- long long ret = NSEC_PER_SEC * b.tv_sec + b.tv_nsec;
-
- ret -= NSEC_PER_SEC * a.tv_sec + a.tv_nsec;
- return ret;
-}
-
int nanosleep_lat_test(int clockid, long long ns)
{
struct timespec start, end, target;
@@ -146,7 +139,7 @@ int main(int argc, char **argv)
continue;
length = 10;
- while (length <= (NSEC_PER_SEC * 10)) {
+ while (length <= (NSEC_PER_SEC * 10LL)) {
ret = nanosleep_lat_test(clockid, length);
if (ret)
break;
@@ -164,3 +157,4 @@ int main(int argc, char **argv)
ksft_finished();
}
+
diff --git a/tools/testing/selftests/timers/valid-adjtimex.c
b/tools/testing/selftests/timers/valid-adjtimex.c
index 6b7801055ad1..a61d4b4739a2 100644
--- a/tools/testing/selftests/timers/valid-adjtimex.c
+++ b/tools/testing/selftests/timers/valid-adjtimex.c
@@ -260,16 +260,16 @@ int validate_set_offset(void)
if (set_offset(-NSEC_PER_SEC - 1, 1))
return -1;
- if (set_offset(5 * NSEC_PER_SEC, 1))
+ if (set_offset(5LL * NSEC_PER_SEC, 1))
return -1;
- if (set_offset(-5 * NSEC_PER_SEC, 1))
+ if (set_offset(-5LL * NSEC_PER_SEC, 1))
return -1;
- if (set_offset(5 * NSEC_PER_SEC + NSEC_PER_SEC / 2, 1))
+ if (set_offset(5LL * NSEC_PER_SEC + NSEC_PER_SEC / 2, 1))
return -1;
- if (set_offset(-5 * NSEC_PER_SEC - NSEC_PER_SEC / 2, 1))
+ if (set_offset(-5LL * NSEC_PER_SEC - NSEC_PER_SEC / 2, 1))
return -1;
if (set_offset(USEC_PER_SEC - 1, 0))
--
2.51.0.384.g4c02a37b29-goog
