[PATCH 1/2] Input; Sanitize event code before modifying bitmaps

Marc Zyngier
2020-08-17T11:27:16Z

When calling into input_set_capability(), the passed event code is
blindly used to set a bit in a number of bitmaps, without checking
whether this actually fits the expected size of the bitmap.

This event code can come from a variety of sources, including devices
masquerading as input devices, only a bit more "programmable".

Instead of taking the raw event code, sanitize it to the actual bitmap
size and output a warning to let the user know.

These checks are, at least in spirit, in keeping with cb222aed03d7
("Input: add safety guards to input_set_keycode()").

Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
drivers/input/input.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 3cfd2c18eebd..1e77cf47aa44 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -1974,14 +1974,18 @@ EXPORT_SYMBOL(input_get_timestamp);
* In addition to setting up corresponding bit in appropriate capability
* bitmap the function also adjusts dev->evbit.
*/
-void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code)
+void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int raw_code)
{
+ unsigned int code = raw_code;
+
switch (type) {
case EV_KEY:
+ code &= KEY_MAX;
__set_bit(code, dev->keybit);
break;

case EV_REL:
+ code &= REL_MAX;
__set_bit(code, dev->relbit);
break;

@@ -1990,26 +1994,32 @@ void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int
if (!dev->absinfo)
return;

+ code &= ABS_MAX;
__set_bit(code, dev->absbit);
break;

case EV_MSC:
+ code &= MSC_MAX;
__set_bit(code, dev->mscbit);
break;

case EV_SW:
+ code &= SW_MAX;
__set_bit(code, dev->swbit);
break;

case EV_LED:
+ code &= LED_MAX;
__set_bit(code, dev->ledbit);
break;

case EV_SND:
+ code &= SND_MAX;
__set_bit(code, dev->sndbit);
break;

case EV_FF:
+ code &= FF_MAX;
__set_bit(code, dev->ffbit);
break;

@@ -2023,6 +2033,10 @@ void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int
return;
}

+ if (unlikely(code != raw_code))
+ pr_warn_ratelimited("%s: Truncated code %d to %d for type %d\n",
+ dev->name, raw_code, code, type);
+
__set_bit(type, dev->evbit);
}
EXPORT_SYMBOL(input_set_capability);
--
2.27.0