Update write() checks to properly detect and handle partial writes. Previously, the write() calls used <= 0 to detect failure. This condition is never true for partial writes (ret > 0 but ret < len), so partial writes were silently treated as success.
Fix this by verifying that write() returns the full expected length and treating any mismatch as failure. Signed-off-by: Vineet Agarwal <[email protected]> Changes in v4: - Simplify write() checks as suggested by Mike Rapoport - Remove temporary variables and use direct comparisons - Use a single len variable --- .../selftests/mm/ksm_functional_tests.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c index 8d874c4754f3..31c06c72203f 100644 --- a/tools/testing/selftests/mm/ksm_functional_tests.c +++ b/tools/testing/selftests/mm/ksm_functional_tests.c @@ -498,6 +498,7 @@ static void test_prctl_fork(void) static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) { int ksm_fd; + size_t len; ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); if (ksm_fd < 0) @@ -506,11 +507,13 @@ static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) if (write(ksm_fd, "1", 1) != 1) return -errno; - if (write(pages_to_scan_fd, pages_to_scan, strlen(pages_to_scan)) <= 0) - return -errno; + len = strlen(pages_to_scan); + if (write(pages_to_scan_fd, pages_to_scan, len) != len) + return -1; - if (write(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0) - return -errno; + len = strlen(sleep_ms); + if (write(sleep_millisecs_fd, sleep_ms, len) != len) + return -1; return 0; } @@ -526,11 +529,11 @@ static int stop_ksmd_and_restore_frequency(void) if (write(ksm_fd, "2", 1) != 1) return -errno; - if (write(pages_to_scan_fd, "100", 3) <= 0) - return -errno; + if (write(pages_to_scan_fd, "100", 3) != 3) + return -1; - if (write(sleep_millisecs_fd, "20", 2) <= 0) - return -errno; + if (write(sleep_millisecs_fd, "20", 2) != 2) + return -1; return 0; } -- 2.54.0
