The dynamically allocted collection stack does not get freed in
all situations. Make sure to also free the collection stack when
using the parser in hid_open_report().

Fixes: 08a8a7cf1459 ("HID: core: do not upper bound the collection stack")
Signed-off-by: Stefan Agner <stefan@agner.ch>
---
Found with kmemleak:

unreferenced object 0xc57f0700 (size 64):
  comm "kworker/0:1", pid 20, jiffies 131383 (age 28.750s)
  hex dump (first 32 bytes):
    02 00 00 00 00 02 00 00 00 00 00 00 00 68 80 c5  .............h..
    80 07 7f c5 01 00 00 00 08 48 80 c5 08 48 80 c5  .........H...H..
  backtrace:
    [<1b437483>] __kmalloc_track_caller+0x1dc/0x300
    [<ecd3baad>] krealloc+0x54/0xc0
    [<c565bd75>] hid_parser_main+0x258/0x2c8
    [<210b9aaa>] hid_open_report+0x134/0x2ac
    [<61cd8964>] hid_generic_probe+0x20/0x38
    [<e02107d6>] hid_device_probe+0xdc/0x13c
    [<334f035e>] really_probe+0x1d8/0x2c4
    [<351dc2c0>] driver_probe_device+0x68/0x184
    [<7e3e3d3c>] __device_attach_driver+0xa0/0xd4
    [<1b053a89>] bus_for_each_drv+0x60/0xc0
    [<732716d8>] __device_attach+0xdc/0x144
    [<dd3a0e76>] device_initial_probe+0x14/0x18
    [<f3a47b76>] bus_probe_device+0x90/0x98
    [<d5a1f0b4>] device_add+0x424/0x62c
    [<46595a15>] hid_add_device+0x108/0x2b8
    [<a0e2824c>] usbhid_probe+0x2d4/0x3bc

 drivers/hid/hid-core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 3da354af7a0a..44a465db3f96 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c

@@ -1039,6 +1039,7 @@ int hid_open_report(struct hid_device *device)
 				hid_err(device, "unbalanced delimiter at end of report description\n");
 				goto err;
 			}
+			kfree(parser->collection_stack);
 			vfree(parser);
 			device->status |= HID_STAT_PARSED;
 			return 0;

@@ -1047,6 +1048,7 @@ int hid_open_report(struct hid_device *device)
 
 	hid_err(device, "item fetching failed at offset %d\n", (int)(end - start));
 err:
+	kfree(parser->collection_stack);
 	vfree(parser);
 	hid_close_report(device);
 	return ret;

-- 
2.18.0