[PATCH 4.19 70/98] Input: MT - limit max slots

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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>

commit 99d3bf5f7377d42f8be60a6b9cb60fb0be34dceb upstream.

syzbot is reporting too large allocation at input_mt_init_slots(), for
num_slots is supplied from userspace using ioctl(UI_DEV_CREATE).

Since nobody knows possible max slots, this patch chose 1024.

Reported-by: syzbot <syzbot+0122fa359a69694395d5@xxxxxxxxxxxxxxxxxxxxxxxxx>
Closes: https://syzkaller.appspot.com/bug?extid=0122fa359a69694395d5
Suggested-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: George Kennedy <george.kennedy@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/input/input-mt.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/input/input-mt.c
+++ b/drivers/input/input-mt.c
@@ -48,6 +48,9 @@ int input_mt_init_slots(struct input_dev
 		return 0;
 	if (mt)
 		return mt->num_slots != num_slots ? -EINVAL : 0;
+	/* Arbitrary limit for avoiding too large memory allocation. */
+	if (num_slots > 1024)
+		return -EINVAL;
 
 	mt = kzalloc(struct_size(mt, slots, num_slots), GFP_KERNEL);
 	if (!mt)






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