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HID: wacom: Have wacom_tpc_irq guard against possible NULL dereference 

The following Smatch complaint was generated in response to commit
2a6cdbd ("HID: wacom: Introduce new 'touch_input' device"):

    drivers/hid/wacom_wac.c:1586 wacom_tpc_irq()
             error: we previously assumed 'wacom->touch_input' could be null (see line 1577)

The 'touch_input' and 'pen_input' variables point to the 'struct input_dev'
used for relaying touch and pen events to userspace, respectively. If a
device does not have a touch interface or pen interface, the associated
input variable is NULL. The 'wacom_tpc_irq()' function is responsible for
forwarding input reports to a more-specific IRQ handler function. An
unknown report could theoretically be mistaken as e.g. a touch report
on a device which does not have a touch interface. This can be prevented
by only calling the pen/touch functions are called when the pen/touch
pointers are valid.

Fixes: 2a6cdbd ("HID: wacom: Introduce new 'touch_input' device")
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Reviewed-by: Ping Cheng <ping.cheng@wacom.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
Jason Gerecke 2017-04-25 11:29:56 -07:00 committed by Jiri Kosina
parent 7af4c727c7
commit 2ac97f0f66
1 changed files with 24 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
drivers/hid/wacom_wac.c
View File

@ -1571,37 +1571,38 @@ static int wacom_tpc_irq(struct wacom_wac *wacom, size_t len)
{
unsigned char *data = wacom->data;
if (wacom->pen_input)
if (wacom->pen_input) {
dev_dbg(wacom->pen_input->dev.parent,
"%s: received report #%d\n", __func__, data[0]);
else if (wacom->touch_input)
if (len == WACOM_PKGLEN_PENABLED ||
data[0] == WACOM_REPORT_PENABLED)
return wacom_tpc_pen(wacom);
}
else if (wacom->touch_input) {
dev_dbg(wacom->touch_input->dev.parent,
"%s: received report #%d\n", __func__, data[0]);
switch (len) {
case WACOM_PKGLEN_TPC1FG:
return wacom_tpc_single_touch(wacom, len);
case WACOM_PKGLEN_TPC2FG:
return wacom_tpc_mt_touch(wacom);
case WACOM_PKGLEN_PENABLED:
return wacom_tpc_pen(wacom);
default:
switch (data[0]) {
case WACOM_REPORT_TPC1FG:
case WACOM_REPORT_TPCHID:
case WACOM_REPORT_TPCST:
case WACOM_REPORT_TPC1FGE:
switch (len) {
case WACOM_PKGLEN_TPC1FG:
return wacom_tpc_single_touch(wacom, len);
case WACOM_REPORT_TPCMT:
case WACOM_REPORT_TPCMT2:
return wacom_mt_touch(wacom);
case WACOM_PKGLEN_TPC2FG:
return wacom_tpc_mt_touch(wacom);
case WACOM_REPORT_PENABLED:
return wacom_tpc_pen(wacom);
default:
switch (data[0]) {
case WACOM_REPORT_TPC1FG:
case WACOM_REPORT_TPCHID:
case WACOM_REPORT_TPCST:
case WACOM_REPORT_TPC1FGE:
return wacom_tpc_single_touch(wacom, len);
case WACOM_REPORT_TPCMT:
case WACOM_REPORT_TPCMT2:
return wacom_mt_touch(wacom);
}
}
}