core: events: correctly handle POLLNVAL in gpiod_line_event_wait()

The only error that can be indicated by ppoll() in the revents field
of struct pollfd when polling a line events file descriptor is
POLLNVAL. It can happen if the user calls close() on said descriptor
after retrieving it with gpiod_line_event_get_fd().

Currently we would act as if there's a line event to read. Make
gpiod_line_event_wait() and its bulk variant return -1 and set errno
to EINVAL in this case.

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>

2 files changed, 52 insertions, 5 deletions

diff --git a/src/lib/core.c b/src/lib/core.c
index 8b89517f..ed802737 100644
--- a/src/lib/core.c
+++ b/src/lib/core.c
@@ -698,16 +698,23 @@ int gpiod_line_event_wait_bulk(struct gpiod_line_bulk *bulk,
 	else if (rv == 0)
 		return 0;
 
-	if (event_bulk) {
+	if (event_bulk)
 		gpiod_line_bulk_init(event_bulk);
 
-		for (off = 0; off < num_lines; off++) {
-			if (fds[off].revents) {
+	for (off = 0; off < num_lines; off++) {
+		if (fds[off].revents) {
+			if (fds[off].revents & POLLNVAL) {
+				errno = EINVAL;
+				return -1;
+			}
+
+			if (event_bulk) {
 				line = gpiod_line_bulk_get_line(bulk, off);
 				gpiod_line_bulk_add(event_bulk, line);
-				if (!--rv)
-					break;
 			}
+
+			if (!--rv)
+				break;
 		}
 	}
 
diff --git a/tests/tests-event.c b/tests/tests-event.c
index 9dbaa658..f91d80fe 100644
--- a/tests/tests-event.c
+++ b/tests/tests-event.c
@@ -9,6 +9,7 @@
 
 #include "gpiod-test.h"
 
+#include <unistd.h>
 #include <errno.h>
 
 static void event_rising_edge_good(void)
@@ -293,3 +294,42 @@ static void event_request_bulk_fail(void)
 TEST_DEFINE(event_request_bulk_fail,
 	    "events - failed bulk request (test reversed release)",
 	    0, { 8 });
+
+static void event_invalid_fd(void)
+{
+	TEST_CLEANUP_CHIP struct gpiod_chip *chip = NULL;
+	struct gpiod_line_bulk bulk = GPIOD_LINE_BULK_INITIALIZER;
+	struct gpiod_line_bulk ev_bulk;
+	struct timespec ts = { 1, 0 };
+	struct gpiod_line *line;
+	int rv, fd;
+
+	chip = gpiod_chip_open(test_chip_path(0));
+	TEST_ASSERT_NOT_NULL(chip);
+
+	line = gpiod_chip_get_line(chip, 5);
+	TEST_ASSERT_NOT_NULL(line);
+
+	rv = gpiod_line_request_both_edges_events(line, TEST_CONSUMER);
+	TEST_ASSERT_RET_OK(rv);
+
+	fd = gpiod_line_event_get_fd(line);
+	close(fd);
+
+	rv = gpiod_line_event_wait(line, &ts);
+	TEST_ASSERT_EQ(rv, -1);
+	TEST_ASSERT_ERRNO_IS(EINVAL);
+
+	/*
+	 * The single line variant calls gpiod_line_event_wait_bulk() with the
+	 * event_bulk argument set to NULL, so test this use case explicitly
+	 * as well.
+	 */
+	gpiod_line_bulk_add(&bulk, line);
+	rv = gpiod_line_event_wait_bulk(&bulk, &ts, &ev_bulk);
+	TEST_ASSERT_EQ(rv, -1);
+	TEST_ASSERT_ERRNO_IS(EINVAL);
+}
+TEST_DEFINE(event_invalid_fd,
+	    "events - gpiod_line_event_wait() error on closed fd",
+	    0, { 8 });