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Commit 04b4b88c authored by Vadim Zaliva's avatar Vadim Zaliva Committed by Dmitry Torokhov
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Input: appletouch - fix integer overflow issue 



When reading data from Geyser 2 touchpads used on post Oct 2005 Apple
PowerBooks the driver was casting X and Y coordinates values to
'signed char'. Testing on one of such PowerBooks I have noticed that
touchpad always generates positive values, but some of them are greater
that 127, and thus, when cast to 'signed char' being interpreted as
a negative.

Such bigger values have been observed infrequently, closer to the
edges of a touchpad, so the problem was not very visible.
Nevertheless, the patch would potentially improve touchpad
driver accuracy.

Signed-off-by: default avatarVadim Zaliva <lord@crocodile.org>
Signed-off-by: default avatarDmitry Torokhov <dtor@mail.ru>
parent 4eb6f91b

drivers/input/mouse/appletouch.c

+3 −3
Original line number Diff line number Diff line
@@ -205,8 +205,8 @@ struct atp { 
	bool			overflow_warned;

	int			x_old;		/* last reported x/y, */

	int			y_old;		/* used for smoothing */

	signed char		xy_cur[ATP_XSENSORS + ATP_YSENSORS];

	signed char		xy_old[ATP_XSENSORS + ATP_YSENSORS];

	u8			xy_cur[ATP_XSENSORS + ATP_YSENSORS];

	u8			xy_old[ATP_XSENSORS + ATP_YSENSORS];

	int			xy_acc[ATP_XSENSORS + ATP_YSENSORS];

	int			idlecount;	/* number of empty packets */

	struct work_struct	work;
@@ -531,7 +531,7 @@ static void atp_complete_geyser_1_2(struct urb *urb) 


	for (i = 0; i < ATP_XSENSORS + ATP_YSENSORS; i++) {

		/* accumulate the change */

		signed char change = dev->xy_old[i] - dev->xy_cur[i];

		int change = dev->xy_old[i] - dev->xy_cur[i];

		dev->xy_acc[i] -= change;



		/* prevent down drifting */