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authorJason Gerecke <killertofu@gmail.com>2017-09-18 19:27:42 +0300
committerJiri Kosina <jkosina@suse.cz>2017-10-02 12:45:29 +0300
commit2a5e597c6bb1b873e473e5f57147e9e5d2755430 (patch)
treecbcc06ee0cf7c42828cee83faf24ea0f8fc27461 /drivers/hid/wacom_sys.c
parent92380b572d95caf48f8424746aeee63c5a2b1922 (diff)
downloadlinux-2a5e597c6bb1b873e473e5f57147e9e5d2755430.tar.xz
HID: wacom: Always increment hdev refcount within wacom_get_hdev_data
The wacom_get_hdev_data function is used to find and return a reference to the "other half" of a Wacom device (i.e., the touch device associated with a pen, or vice-versa). To ensure these references are properly accounted for, the function is supposed to automatically increment the refcount before returning. This was not done, however, for devices which have pen & touch on different interfaces of the same USB device. This can lead to a WARNING ("refcount_t: underflow; use-after-free") when removing the module or device as we call kref_put() more times than kref_get(). Triggering an "actual" use- after-free would be difficult since both devices will disappear nearly- simultaneously. To silence this warning and prevent the potential error, we need to increment the refcount for all cases within wacom_get_hdev_data. Fixes: 41372d5d40 ("HID: wacom: Augment 'oVid' and 'oPid' with heuristics for HID_GENERIC") Cc: <stable@vger.kernel.org> # v4.9+ Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com> Reviewed-by: Ping Cheng <ping.cheng@wacom.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid/wacom_sys.c')
-rw-r--r--drivers/hid/wacom_sys.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c
index 735bfbbcaa82..906e654fb0ba 100644
--- a/drivers/hid/wacom_sys.c
+++ b/drivers/hid/wacom_sys.c
@@ -668,8 +668,10 @@ static struct wacom_hdev_data *wacom_get_hdev_data(struct hid_device *hdev)
/* Try to find an already-probed interface from the same device */
list_for_each_entry(data, &wacom_udev_list, list) {
- if (compare_device_paths(hdev, data->dev, '/'))
+ if (compare_device_paths(hdev, data->dev, '/')) {
+ kref_get(&data->kref);
return data;
+ }
}
/* Fallback to finding devices that appear to be "siblings" */