diff mbox series

[v1,1/1] Input: ALPS - bail out when device path can't fit buffer

Message ID 20250422185645.1949391-1-andriy.shevchenko@linux.intel.com
State New
Headers show
Series [v1,1/1] Input: ALPS - bail out when device path can't fit buffer | expand

Commit Message

Andy Shevchenko April 22, 2025, 6:56 p.m. UTC 
When creating a physical device name in the driver the snprintf() takes
an up to 32 characters argument along with the additional 8 characters
and tries to pack this into 32 bytes array. GCC complains about that
when build with `make W=1`:

drivers/input/mouse/alps.c:1411:9: note: ‘snprintf’ output between 8 and 39 bytes into a destination of size 32
 1411 |         snprintf(priv->phys3, sizeof(priv->phys3), "%s/%s",
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1412 |                  psmouse->ps2dev.serio->phys,
      |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 1413 |                  (priv->dev2 ? "input2" : "input1"));
      |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

drivers/input/mouse/alps.c:3106:17: note: ‘snprintf’ output between 8 and 39 bytes into a destination of size 32
 3106 |                 snprintf(priv->phys2, sizeof(priv->phys2), "%s/input1",
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 3107 |                          psmouse->ps2dev.serio->phys);
      |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fix these by checking for the potential overflow.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/input/mouse/alps.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

Comments

Dmitry Torokhov April 28, 2025, 11:30 p.m. UTC | #1 
Hi Andy,

On Tue, Apr 22, 2025 at 09:56:45PM +0300, Andy Shevchenko wrote:
> @@ -3094,6 +3101,16 @@ int alps_init(struct psmouse *psmouse)
>  
>  	if (priv->flags & ALPS_DUALPOINT) {
>  		struct input_dev *dev2;
> +		int n;
> +
> +		n = snprintf(priv->phys2, sizeof(priv->phys2), "%s/input1",
> +			     psmouse->ps2dev.serio->phys);
> +		if (n >= sizeof(priv->phys2)) {
> +			psmouse_err(psmouse,
> +				    "failed to prepare path to the trackstick device\n");
> +			error = -E2BIG;
> +			goto init_fail;

So you just broke touchpad of some poor guy who had it working just fine 
for many years. For maximum impact you should add BUG() or panic()
here.

In all seriousness, it is OK to have truncated phys, rarely anyone looks
at it and if we get a report of it being truncated then we can consider
addressing the size (or we can decide to live with it truncated).

Thanks.
diff mbox series

Patch

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 0bd7b09b0aa3..e76dcb19fa72 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -1401,6 +1401,16 @@  static int alps_do_register_bare_ps2_mouse(struct alps_data *priv)
 	struct psmouse *psmouse = priv->psmouse;
 	struct input_dev *dev3;
 	int error;
+	int n;
+
+	n = snprintf(priv->phys3, sizeof(priv->phys3), "%s/%s",
+		     psmouse->ps2dev.serio->phys,
+		     priv->dev2 ? "input2" : "input1");
+	if (n >= sizeof(priv->phys3)) {
+		psmouse_err(psmouse,
+			    "failed to prepare path to the secondary device\n");
+		return -E2BIG;
+	}
 
 	dev3 = input_allocate_device();
 	if (!dev3) {
@@ -1408,9 +1418,6 @@  static int alps_do_register_bare_ps2_mouse(struct alps_data *priv)
 		return -ENOMEM;
 	}
 
-	snprintf(priv->phys3, sizeof(priv->phys3), "%s/%s",
-		 psmouse->ps2dev.serio->phys,
-		 (priv->dev2 ? "input2" : "input1"));
 	dev3->phys = priv->phys3;
 
 	/*
@@ -3094,6 +3101,16 @@  int alps_init(struct psmouse *psmouse)
 
 	if (priv->flags & ALPS_DUALPOINT) {
 		struct input_dev *dev2;
+		int n;
+
+		n = snprintf(priv->phys2, sizeof(priv->phys2), "%s/input1",
+			     psmouse->ps2dev.serio->phys);
+		if (n >= sizeof(priv->phys2)) {
+			psmouse_err(psmouse,
+				    "failed to prepare path to the trackstick device\n");
+			error = -E2BIG;
+			goto init_fail;
+		}
 
 		dev2 = input_allocate_device();
 		if (!dev2) {
@@ -3103,8 +3120,6 @@  int alps_init(struct psmouse *psmouse)
 			goto init_fail;
 		}
 
-		snprintf(priv->phys2, sizeof(priv->phys2), "%s/input1",
-			 psmouse->ps2dev.serio->phys);
 		dev2->phys = priv->phys2;
 
 		/*