fix(esp_libc): reject out-of-range adjtime() deltas instead of overflowing

The adjtime() wrapper stored the microsecond offset into the 32-bit
`long` timex.offset field without checking for overflow. A large delta
(e.g. 400 days) was computed in 64-bit and silently truncated when
assigned, wrapping into a small value that passed the ~35 minute range
check. adjtime() then returned 0 instead of the expected -1.

Compute the offset in int64_t and reject values that do not fit in the
timex.offset field with EINVAL. Add a regression test for a multi-day delta.

Closes https://github.com/espressif/esp-idf/issues/19051

components/esp_libc/src/time.c

@@ -189,8 +189,15 @@ WEAK_UNLESS_TIMEFUNC_IMPL int adjtime(const struct timeval *delta, struct timeva
     struct timex tx = {0};
 
     if (delta != NULL) {
+        // Reject deltas that do not fit in the 32-bit struct timex.offset (µs) field,
+        // otherwise the value would be silently truncated and pass the range check.
+        int64_t offset_us = (int64_t)delta->tv_sec * 1000000LL + delta->tv_usec;
+        if (offset_us > LONG_MAX || offset_us < LONG_MIN) {
+            errno = EINVAL;
+            return -1;
+        }
         tx.modes = ADJ_OFFSET_SINGLESHOT;
-        tx.offset = delta->tv_sec * 1000000L + delta->tv_usec;
+        tx.offset = (long)offset_us;
     } else {
         tx.modes = ADJ_OFFSET_SS_READ;
     }

components/esp_libc/test_apps/newlib/main/test_time.c

@@ -192,6 +192,18 @@ void test_adjtime_function(test_adjtime_mode_t mode, test_clock_adjtime_units_t
         TEST_ASSERT_EQUAL(realtime_adjtime_wrapper(&tv_delta, &tv_outdelta, mode, units), -1);
     }
 
+    // a multi-day delta must be rejected, not silently
+    // truncated into the 32-bit timex.offset (µs) field and applied as a small slew.
+    if (mode == TEST_ADJTIME_MODE_LEGACY) {
+        tv_delta.tv_sec = 400L * 24 * 60 * 60; // 400 days
+        tv_delta.tv_usec = 123456;
+        TEST_ASSERT_EQUAL(realtime_adjtime_wrapper(&tv_delta, NULL, mode, units), -1);
+
+        tv_delta.tv_sec = -400L * 24 * 60 * 60;
+        tv_delta.tv_usec = -123456;
+        TEST_ASSERT_EQUAL(realtime_adjtime_wrapper(&tv_delta, NULL, mode, units), -1);
+    }
+
     tv_delta.tv_sec = 0;
     tv_delta.tv_usec = -900000;
     TEST_ASSERT_EQUAL(realtime_adjtime_wrapper(&tv_delta, &tv_outdelta, mode, units), 0);