[PATCH v2 libevdev] Drop invalid ABS_MT_TRACKING_ID changes
Peter Hutterer
peter.hutterer at who-t.net
Wed Apr 2 20:39:05 PDT 2014
Follow-up to
commit 41334b5b40cd5456f5f584b55d8888aaafa1f26e
Author: Peter Hutterer <peter.hutterer at who-t.net>
Date: Thu Mar 6 11:54:00 2014 +1000
If the tracking ID changes during SYN_DROPPED, terminate the touch first
In normal mode, we may get double tracking ID events in the same slot, but
only if we either have a user-generated event sequence (uinput) or a malicious
device that tries to send data on a slot > dev->num_slots.
Since the client is unlikely to be able to handle these events, discard the
ABS_MT_TRACKING_ID completely. This is a bug somewhere in the stack, so
complain and hobble on along.
Note: the kernel doesn't allow that, but we cap to num_slots anyway, see
66fee1bec4c4b021e1b54adcd775cf6e2aa84869.
Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
Luckily Benjamin asked for the test for double -1 tracking IDs, it exposed a
bug in the code and a bug in the test that covered it up. In the previous
version sanitize_event() would return -1 but we wouldn't actually discard
ignored, so it looked like a success.
Changes to v1:
- use an enum for sanitize_event return codes
- actually discard the event this time and return the next event in line (if
any)
- add a test for double -1 tracking IDs
ignored in the test, so it all looked good.
libevdev/libevdev.c | 47 ++++++++++---
test/test-libevdev-events.c | 160 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 196 insertions(+), 11 deletions(-)
diff --git a/libevdev/libevdev.c b/libevdev/libevdev.c
index 119f18f..96bd41b 100644
--- a/libevdev/libevdev.c
+++ b/libevdev/libevdev.c
@@ -36,6 +36,12 @@
#define MAXEVENTS 64
+enum event_filter_status {
+ EVENT_FILTER_NONE, /**< Event untouched by filters */
+ EVENT_FILTER_MODIFIED, /**< Event was modified */
+ EVENT_FILTER_DISCARD, /**< Discard current event */
+};
+
static int sync_mt_state(struct libevdev *dev, int create_events);
static inline int*
@@ -880,10 +886,11 @@ read_more_events(struct libevdev *dev)
/**
* Sanitize/modify events where needed.
- * @return 0 if untouched, 1 if modified.
*/
-static inline int
-sanitize_event(const struct libevdev *dev, struct input_event *ev)
+static inline enum event_filter_status
+sanitize_event(const struct libevdev *dev,
+ struct input_event *ev,
+ enum SyncState sync_state)
{
if (unlikely(dev->num_slots > -1 &&
libevdev_event_is_code(ev, EV_ABS, ABS_MT_SLOT) &&
@@ -892,16 +899,32 @@ sanitize_event(const struct libevdev *dev, struct input_event *ev)
"Capping to announced max slot number %d.\n",
dev->name, ev->value, dev->num_slots - 1);
ev->value = dev->num_slots - 1;
- return 1;
+ return EVENT_FILTER_MODIFIED;
+
+ /* Drop any invalid tracking IDs, they are only supposed to go from
+ N to -1 or from -1 to N. Never from -1 to -1, or N to M. Very
+ unlikely to ever happen from a real device.
+ */
+ } else if (unlikely(sync_state == SYNC_NONE &&
+ dev->num_slots > -1 &&
+ libevdev_event_is_code(ev, EV_ABS, ABS_MT_TRACKING_ID) &&
+ ((ev->value == -1 &&
+ *slot_value(dev, dev->current_slot, ABS_MT_TRACKING_ID) == -1) ||
+ (ev->value != -1 &&
+ *slot_value(dev, dev->current_slot, ABS_MT_TRACKING_ID) != -1)))) {
+ log_bug("Device \"%s\" received a double tracking ID %d in slot %d.\n",
+ dev->name, ev->value, dev->current_slot);
+ return EVENT_FILTER_DISCARD;
}
- return 0;
+ return EVENT_FILTER_NONE;
}
LIBEVDEV_EXPORT int
libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_event *ev)
{
int rc = LIBEVDEV_READ_STATUS_SUCCESS;
+ enum event_filter_status filter_status;
if (!dev->initialized) {
log_bug("device not initialized. call libevdev_set_fd() first\n");
@@ -934,8 +957,8 @@ libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_event
of the device too */
while (queue_shift(dev, &e) == 0) {
dev->queue_nsync--;
- sanitize_event(dev, &e);
- update_state(dev, &e);
+ if (sanitize_event(dev, &e, dev->sync_state) != EVENT_FILTER_DISCARD)
+ update_state(dev, &e);
}
dev->sync_state = SYNC_NONE;
@@ -965,11 +988,13 @@ libevdev_next_event(struct libevdev *dev, unsigned int flags, struct input_event
if (queue_shift(dev, ev) != 0)
return -EAGAIN;
- sanitize_event(dev, ev);
- update_state(dev, ev);
+ filter_status = sanitize_event(dev, ev, dev->sync_state);
+ if (filter_status != EVENT_FILTER_DISCARD)
+ update_state(dev, ev);
/* if we disabled a code, get the next event instead */
- } while(!libevdev_has_event_code(dev, ev->type, ev->code));
+ } while(filter_status == EVENT_FILTER_DISCARD ||
+ !libevdev_has_event_code(dev, ev->type, ev->code));
rc = LIBEVDEV_READ_STATUS_SUCCESS;
if (ev->type == EV_SYN && ev->code == SYN_DROPPED) {
@@ -1163,7 +1188,7 @@ libevdev_set_event_value(struct libevdev *dev, unsigned int type, unsigned int c
e.code = code;
e.value = value;
- if (sanitize_event(dev, &e))
+ if (sanitize_event(dev, &e, SYNC_NONE) != EVENT_FILTER_NONE)
return -1;
switch(type) {
diff --git a/test/test-libevdev-events.c b/test/test-libevdev-events.c
index fda7617..dc412a7 100644
--- a/test/test-libevdev-events.c
+++ b/test/test-libevdev-events.c
@@ -1424,6 +1424,164 @@ START_TEST(test_mt_slot_ranges_invalid)
}
END_TEST
+START_TEST(test_mt_tracking_id_discard)
+{
+ struct uinput_device* uidev;
+ struct libevdev *dev;
+ int rc;
+ struct input_event ev;
+ struct input_absinfo abs[6];
+
+ memset(abs, 0, sizeof(abs));
+ abs[0].value = ABS_X;
+ abs[0].maximum = 1000;
+ abs[1].value = ABS_MT_POSITION_X;
+ abs[1].maximum = 1000;
+
+ abs[2].value = ABS_Y;
+ abs[2].maximum = 1000;
+ abs[3].value = ABS_MT_POSITION_Y;
+ abs[3].maximum = 1000;
+
+ abs[4].value = ABS_MT_SLOT;
+ abs[4].maximum = 10;
+ abs[5].value = ABS_MT_TRACKING_ID;
+ abs[5].maximum = 500;
+
+ rc = test_create_abs_device(&uidev, &dev,
+ 6, abs,
+ EV_SYN, SYN_REPORT,
+ -1);
+
+ uinput_device_event(uidev, EV_ABS, ABS_MT_SLOT, 1);
+ uinput_device_event(uidev, EV_ABS, ABS_MT_TRACKING_ID, 1);
+ uinput_device_event(uidev, EV_SYN, SYN_REPORT, 0);
+
+ /* second tracking ID on same slot */
+ uinput_device_event(uidev, EV_ABS, ABS_MT_TRACKING_ID, 2);
+ uinput_device_event(uidev, EV_SYN, SYN_REPORT, 0);
+
+ libevdev_set_log_function(test_logfunc_ignore_error, NULL);
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_ABS);
+ ck_assert_int_eq(ev.code, ABS_MT_SLOT);
+ ck_assert_int_eq(ev.value, 1);
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_ABS);
+ ck_assert_int_eq(ev.code, ABS_MT_TRACKING_ID);
+ ck_assert_int_eq(ev.value, 1);
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_SYN);
+ ck_assert_int_eq(ev.code, SYN_REPORT);
+ ck_assert_int_eq(ev.value, 0);
+
+ /* expect tracking ID discarded */
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_SYN);
+ ck_assert_int_eq(ev.code, SYN_REPORT);
+ ck_assert_int_eq(ev.value, 0);
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, -EAGAIN);
+
+ libevdev_set_log_function(test_logfunc_abort_on_error, NULL);
+
+ uinput_device_free(uidev);
+ libevdev_free(dev);
+}
+END_TEST
+
+START_TEST(test_mt_tracking_id_discard_neg_1)
+{
+ struct uinput_device* uidev;
+ struct libevdev *dev;
+ int rc;
+ struct input_event ev;
+ struct input_absinfo abs[6];
+ int pipefd[2];
+ struct input_event events[] = {
+ { .type = EV_ABS, .code = ABS_MT_TRACKING_ID, .value = -1 },
+ { .type = EV_SYN, .code = SYN_REPORT, .value = 0 },
+ };
+
+ rc = pipe2(pipefd, O_NONBLOCK);
+ ck_assert_int_eq(rc, 0);
+
+ memset(abs, 0, sizeof(abs));
+ abs[0].value = ABS_X;
+ abs[0].maximum = 1000;
+ abs[1].value = ABS_MT_POSITION_X;
+ abs[1].maximum = 1000;
+
+ abs[2].value = ABS_Y;
+ abs[2].maximum = 1000;
+ abs[3].value = ABS_MT_POSITION_Y;
+ abs[3].maximum = 1000;
+
+ abs[4].value = ABS_MT_SLOT;
+ abs[4].maximum = 10;
+ abs[5].value = ABS_MT_TRACKING_ID;
+ abs[5].maximum = 500;
+
+ rc = test_create_abs_device(&uidev, &dev,
+ 6, abs,
+ EV_SYN, SYN_REPORT,
+ -1);
+ uinput_device_event(uidev, EV_ABS, ABS_MT_SLOT, 1);
+ uinput_device_event(uidev, EV_ABS, ABS_MT_TRACKING_ID, 1);
+ uinput_device_event(uidev, EV_SYN, SYN_REPORT, 0);
+
+ while (libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev) != -EAGAIN)
+ ;
+
+ libevdev_set_log_function(test_logfunc_ignore_error, NULL);
+
+ /* two -1 tracking ids, need to use the pipe here, the kernel will
+ filter it otherwise */
+ libevdev_change_fd(dev, pipefd[0]);
+
+ rc = write(pipefd[1], events, sizeof(events));
+ ck_assert_int_eq(rc, sizeof(events));
+ rc = write(pipefd[1], events, sizeof(events));
+ ck_assert_int_eq(rc, sizeof(events));
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_ABS);
+ ck_assert_int_eq(ev.code, ABS_MT_TRACKING_ID);
+ ck_assert_int_eq(ev.value, -1);
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_SYN);
+ ck_assert_int_eq(ev.code, SYN_REPORT);
+ ck_assert_int_eq(ev.value, 0);
+
+ /* expect second tracking ID discarded */
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, LIBEVDEV_READ_STATUS_SUCCESS);
+ ck_assert_int_eq(ev.type, EV_SYN);
+ ck_assert_int_eq(ev.code, SYN_REPORT);
+ ck_assert_int_eq(ev.value, 0);
+
+ rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
+ ck_assert_int_eq(rc, -EAGAIN);
+
+ libevdev_set_log_function(test_logfunc_abort_on_error, NULL);
+
+ uinput_device_free(uidev);
+ libevdev_free(dev);
+}
+END_TEST
+
START_TEST(test_ev_rep_values)
{
struct uinput_device* uidev;
@@ -1719,6 +1877,8 @@ libevdev_events(void)
tcase_add_test(tc, test_mt_event_values);
tcase_add_test(tc, test_mt_event_values_invalid);
tcase_add_test(tc, test_mt_slot_ranges_invalid);
+ tcase_add_test(tc, test_mt_tracking_id_discard);
+ tcase_add_test(tc, test_mt_tracking_id_discard_neg_1);
tcase_add_test(tc, test_ev_rep_values);
suite_add_tcase(s, tc);
--
1.9.0
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