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Subject[PATCH] Input: add safety guards to input_set_keycode()
If we happen to have a garbage in input device's keycode table with values
too big we'll end up doing clear_bit() with offset way outside of our
bitmaps, damaging other objects within an input device or even outside of
it. Let's add sanity checks to the returned old keycodes.

Reported-by: syzbot+c769968809f9359b07aa@syzkaller.appspotmail.com
Reported-by: syzbot+76f3a30e88d256644c78@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
drivers/input/input.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 55086279d044..ee6c3234df36 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -878,16 +878,18 @@ static int input_default_setkeycode(struct input_dev *dev,
}
}

- __clear_bit(*old_keycode, dev->keybit);
- __set_bit(ke->keycode, dev->keybit);
-
- for (i = 0; i < dev->keycodemax; i++) {
- if (input_fetch_keycode(dev, i) == *old_keycode) {
- __set_bit(*old_keycode, dev->keybit);
- break; /* Setting the bit twice is useless, so break */
+ if (*old_keycode <= KEY_MAX) {
+ __clear_bit(*old_keycode, dev->keybit);
+ for (i = 0; i < dev->keycodemax; i++) {
+ if (input_fetch_keycode(dev, i) == *old_keycode) {
+ __set_bit(*old_keycode, dev->keybit);
+ /* Setting the bit twice is useless, so break */
+ break;
+ }
}
}

+ __set_bit(ke->keycode, dev->keybit);
return 0;
}

@@ -943,9 +945,13 @@ int input_set_keycode(struct input_dev *dev,
* Simulate keyup event if keycode is not present
* in the keymap anymore
*/
- if (test_bit(EV_KEY, dev->evbit) &&
- !is_event_supported(old_keycode, dev->keybit, KEY_MAX) &&
- __test_and_clear_bit(old_keycode, dev->key)) {
+ if (old_keycode > KEY_MAX) {
+ dev_warn(dev->dev.parent ?: &dev->dev,
+ "%s: got too big old keycode %#x\n",
+ __func__, old_keycode);
+ } else if (test_bit(EV_KEY, dev->evbit) &&
+ !is_event_supported(old_keycode, dev->keybit, KEY_MAX) &&
+ __test_and_clear_bit(old_keycode, dev->key)) {
struct input_value vals[] = {
{ EV_KEY, old_keycode, 0 },
input_value_sync
--
2.24.0.393.g34dc348eaf-goog

--
Dmitry

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