[PATCH 4.9 46/62] HID: fix error message in hid_open_report()

Greg Kroah-Hartman
2019-11-04T22:26:38Z

From: Michał Mirosław <mirq-linux@rere.qmqm.pl>

commit b3a81c777dcb093020680490ab970d85e2f6f04f upstream.

On HID report descriptor parsing error the code displays bogus
pointer instead of error offset (subtracts start=NULL from end).
Make the message more useful by displaying correct error offset
and include total buffer size for reference.

This was carried over from ancient times - "Fixed" commit just
promoted the message from DEBUG to ERROR.

Cc: stable@vger.kernel.org
Fixes: 8c3d52fc393b ("HID: make parser more verbose about parsing errors by default")
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hid/hid-core.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -959,6 +959,7 @@ int hid_open_report(struct hid_device *d
__u8 *start;
__u8 *buf;
__u8 *end;
+ __u8 *next;
int ret;
static int (*dispatch_type[])(struct hid_parser *parser,
struct hid_item *item) = {
@@ -1012,7 +1013,8 @@ int hid_open_report(struct hid_device *d
device->collection_size = HID_DEFAULT_NUM_COLLECTIONS;

ret = -EINVAL;
- while ((start = fetch_item(start, end, &item)) != NULL) {
+ while ((next = fetch_item(start, end, &item)) != NULL) {
+ start = next;

if (item.format != HID_ITEM_FORMAT_SHORT) {
hid_err(device, "unexpected long global item\n");
@@ -1041,7 +1043,8 @@ int hid_open_report(struct hid_device *d
}
}

- hid_err(device, "item fetching failed at offset %d\n", (int)(end - start));
+ hid_err(device, "item fetching failed at offset %u/%u\n",
+ size - (unsigned int)(end - start), size);
err:
vfree(parser);
hid_close_report(device);