| Message ID | 20170918162742.10717-1-killertofu@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 18, 2017 at 9:27 AM, Jason Gerecke <killertofu@gmail.com> wrote: > 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> Cheers, Ping > --- > drivers/hid/wacom_sys.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > 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" */ > -- > 2.14.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 26 Sep 2017, Jason Gerecke wrote:
> Haven't seen any activity on this patch, so sending a reminder.
Yeah, I have been travelling for past 3 weeks and acumulated quite some
backlog, sorry. Everything pending should be processed by the end of this
week.
On Mon, 18 Sep 2017, Jason Gerecke wrote: > 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> Applied to for-4.14/upstream-fixes.
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" */
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> --- drivers/hid/wacom_sys.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)