HID: pidff: Fix possible null pointer dereference

As reported by Dan Carpenter, if the axes_enable field wasn't found,
trying to find the axes themselves will result in a null pointer
dereference. This could only occur with a broken PID descriptor, but
it's worth protecting from.

Exit early if the axes_enable wasn't found AND add a gate to the
pidff_find_special_keys to exit early if the passed HID field is null.
This will protect again null dereferencing in the future and properly
return 0 found special keys.

Fixes: 1d72e7bd340b ("HID: pidff: Add support for AXES_ENABLE field")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/usbhid/hid-pidff.c b/drivers/hid/usbhid/hid-pidff.c
index 0342c0a3f476d26e8d8c38ca943575d43dd33275..edd61ef50e16a2c2ea287580b1b62071555c4ba9 100644 (file)
--- a/drivers/hid/usbhid/hid-pidff.c
+++ b/drivers/hid/usbhid/hid-pidff.c
@@ -1194,6 +1194,9 @@ static int pidff_find_special_keys(int *keys, struct hid_field *fld,
 {
        int found = 0;
 
+       if (!fld)
+               return 0;
+
        for (int i = 0; i < count; i++) {
                keys[i] = pidff_find_usage(fld, usage_page | usagetable[i]) + 1;
                if (keys[i])
@@ -1299,11 +1302,13 @@ static int pidff_find_special_fields(struct pidff_device *pidff)
                return -1;
        }
 
-       if (!pidff->axes_enable)
+       if (!pidff->axes_enable) {
                hid_info(pidff->hid, "axes enable field not found!\n");
-       else
-               hid_dbg(pidff->hid, "axes enable report count: %u\n",
-                       pidff->axes_enable->report_count);
+               return 0;
+       }
+
+       hid_dbg(pidff->hid, "axes enable report count: %u\n",
+               pidff->axes_enable->report_count);
 
        uint found = PIDFF_FIND_GENERAL_DESKTOP(direction_axis_id, axes_enable,
                                                direction_axis);
@@ -1311,7 +1316,7 @@ static int pidff_find_special_fields(struct pidff_device *pidff)
        pidff->axis_count = found;
        hid_dbg(pidff->hid, "found direction axes: %u", found);
 
-       for (int i = 0; i < sizeof(pidff_direction_axis); i++) {
+       for (int i = 0; i < ARRAY_SIZE(pidff_direction_axis); i++) {
                if (!pidff->direction_axis_id[i])
                        continue;