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Fri, 29 May 2026 14:44:44 -0700 (PDT) Date: Fri, 29 May 2026 14:44:41 -0700 From: Dmitry Torokhov To: Jinmo Yang Cc: Ping Cheng , Jason Gerecke , Jiri Kosina , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] HID: wacom: fix NULL pointer dereference in wacom_intuos_pad() Message-ID: References: <20260523150101.611473-1-jinmo44.yang@gmail.com> <20260523150619.615565-1-jinmo44.yang@gmail.com> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260523150619.615565-1-jinmo44.yang@gmail.com> On Sun, May 24, 2026 at 12:06:19AM +0900, Jinmo Yang wrote: > wacom_intuos_pad() dereferences wacom->pad_input without a NULL check. > When a Wacom tablet is created via UHID with parameters that route > through wacom_bpt_irq() -> wacom_intuos_irq() -> wacom_intuos_pad(), > but probe did not allocate pad_input, the call to > wacom_report_numbered_buttons() passes a NULL input_dev, causing a > general protection fault in input_get_drvdata(). > > Add a NULL check for pad_input at the top of wacom_intuos_pad() to > bail out early when the pad input device was not set up. > > The bug was found by syzkaller on linux-next 7.1.0-rc4 (next-20260522): > > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000052 > KASAN: null-ptr-deref in range [0x0000000000000290-0x0000000000000297] > RIP: 0010:input_get_drvdata include/linux/input.h:390 [inline] > RIP: 0010:wacom_report_numbered_buttons+0x37/0x210 drivers/hid/wacom_wac.c:4210 > Call Trace: > wacom_intuos_pad drivers/hid/wacom_wac.c:643 [inline] > wacom_intuos_irq+0x29a/0x32b0 drivers/hid/wacom_wac.c:1042 > wacom_bpt_irq drivers/hid/wacom_wac.c:3275 [inline] > wacom_wac_irq+0x12ed/0xaef0 drivers/hid/wacom_wac.c:3545 > wacom_raw_event+0x677/0xa90 drivers/hid/wacom_sys.c:184 > __hid_input_report.constprop.0+0x39a/0x4d0 drivers/hid/hid-core.c:2161 > uhid_dev_input2 drivers/hid/uhid.c:618 [inline] > uhid_char_write+0xa8a/0xfa0 drivers/hid/uhid.c:776 > > Also confirmed on a Pixel 9 Pro (Android 16, kernel 6.1.124) where > it causes an immediate kernel panic and reboot via /dev/uhid without > requiring root privileges: > > KP: Oops: Fatal exception: comm:wacom_27qhdt > Reboot reason: 0xbaba - Kernel PANIC > > Reproducer (unprivileged): > open("/dev/uhid", O_RDWR) > write(fd, UHID_CREATE2{vendor=0x056a, product=0x0020}) > write(fd, UHID_INPUT2{report_id=0x0c, size=10}) > > Fixes: c7f0522a1ad1 ("HID: wacom: Slim down wacom_intuos_pad processing") > Signed-off-by: Jinmo Yang > --- > drivers/hid/wacom_wac.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c > index da1f0ea85..251ddda3e 100644 > --- a/drivers/hid/wacom_wac.c > +++ b/drivers/hid/wacom_wac.c > @@ -515,7 +515,6 @@ static int wacom_intuos_pad(struct wacom_wac *wacom) > struct wacom_features *features = &wacom->features; > unsigned char *data = wacom->data; > struct input_dev *input = wacom->pad_input; > - int i; > int buttons = 0, nbuttons = features->numbered_buttons; > int keys = 0, nkeys = 0; > int ring1 = 0, ring2 = 0; > @@ -523,6 +522,10 @@ static int wacom_intuos_pad(struct wacom_wac *wacom) > bool prox = false; > bool wrench = false, keyboard = false, mute_touch = false, menu = false, > info = false; > + int i; > + > + if (!input) > + return 0; > > /* pad packets. Works as a second tool and is always in prox */ > if (!(data[0] == WACOM_REPORT_INTUOSPAD || data[0] == WACOM_REPORT_INTUOS5PAD || I think there are many more places in the driver where it used wacom->pad_input without verifying that it exists. Thanks. -- Dmitry