Update write() checks to properly detect and handle partial writes. Previously, partial writes (ret > 0 && ret != len) could be treated as success because write() does not set errno in this case and the code returned -errno. This could result in returning 0 and incorrectly signaling 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 v3: - Simplify error handling as suggested by reviewer - Return -1 when write() does not complete fully - Rebase patch against base tree --- .../selftests/mm/ksm_functional_tests.c | 27 +++++++++++++------ 1 file changed, 19 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..4abd98be3f59 100644 --- a/tools/testing/selftests/mm/ksm_functional_tests.c +++ b/tools/testing/selftests/mm/ksm_functional_tests.c @@ -498,6 +498,8 @@ static void test_prctl_fork(void) static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) { int ksm_fd; + ssize_t ret; + size_t len, sleep_len; ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); if (ksm_fd < 0) @@ -506,11 +508,17 @@ 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(sleep_millisecs_fd, sleep_ms, strlen(sleep_ms)) <= 0) - return -errno; + ret = write(pages_to_scan_fd, pages_to_scan, len); + if (ret != len) + return -1; + + sleep_len = strlen(sleep_ms); + + ret = write(sleep_millisecs_fd, sleep_ms, sleep_len); + if (ret != sleep_len) + return -1; return 0; } @@ -518,6 +526,7 @@ static int start_ksmd_and_set_frequency(char *pages_to_scan, char *sleep_ms) static int stop_ksmd_and_restore_frequency(void) { int ksm_fd; + ssize_t ret; ksm_fd = open("/sys/kernel/mm/ksm/run", O_RDWR); if (ksm_fd < 0) @@ -526,11 +535,13 @@ 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; + ret = write(pages_to_scan_fd, "100", 3); + if (ret != 3) + return -1; - if (write(sleep_millisecs_fd, "20", 2) <= 0) - return -errno; + ret = write(sleep_millisecs_fd, "20", 2); + if (ret != 2) + return -1; return 0; } -- 2.54.0
