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Sun, 26 Apr 2026 21:22:23 -0700 (PDT) Date: Sun, 26 Apr 2026 21:22:21 -0700 From: Dmitry Torokhov To: Greg Kroah-Hartman Cc: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, stable Subject: Re: [PATCH] Input: xpad - reject short Xbox One packets before len-relative share-button index Message-ID: References: <2026042014-freestyle-deluxe-48e4@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@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: <2026042014-freestyle-deluxe-48e4@gregkh> Hi Greg, On Mon, Apr 20, 2026 at 05:53:15PM +0200, Greg Kroah-Hartman wrote: > xpadone_process_packet() receives len directly from urb->actual_length > and uses it to index the share-button byte at data[len - 18] or > data[len - 26]. Since both len and data[0] are under the device's > control, a broken controller can send a GIP_CMD_INPUT packet with > actual_length < 18 (e.g. 5 bytes) and reach this code path, causing > accesses beyond the actual array. > > Since len is u32, 5 - 26 wraps to 0xFFFFFFEB, and data[0xFFFFFFEB] can > dereference about 4 GiB past the 64-byte usb_alloc_coherent() idata > buffer. On a KASAN system this is an immediate splat otherwise the read > will either fault on an unmapped page (DoS) or pull a bit from arbitrary > kernel memory and report it as KEY_RECORD. > > Fix this all up by properly bounds checking the value provided by the > device. > > Cc: Dmitry Torokhov > Fixes: 4ef46367073b ("Input: xpad - fix Share button on Xbox One controllers") > Cc: stable > Assisted-by: gkh_clanker_t1000 > Signed-off-by: Greg Kroah-Hartman > --- > drivers/input/joystick/xpad.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/drivers/input/joystick/xpad.c b/drivers/input/joystick/xpad.c > index d6fc3d6006bb..7d99fe0ecf91 100644 > --- a/drivers/input/joystick/xpad.c > +++ b/drivers/input/joystick/xpad.c > @@ -1110,10 +1110,13 @@ static void xpadone_process_packet(struct usb_xpad *xpad, u16 cmd, unsigned char > input_report_key(dev, BTN_START, data[4] & BIT(2)); > input_report_key(dev, BTN_SELECT, data[4] & BIT(3)); > if (xpad->mapping & MAP_SHARE_BUTTON) { > - if (xpad->mapping & MAP_SHARE_OFFSET) > - input_report_key(dev, KEY_RECORD, data[len - 26] & BIT(0)); > - else > - input_report_key(dev, KEY_RECORD, data[len - 18] & BIT(0)); > + if (xpad->mapping & MAP_SHARE_OFFSET) { > + if (len >= 26) > + input_report_key(dev, KEY_RECORD, data[len - 26] & BIT(0)); > + } else { > + if (len >= 18) > + input_report_key(dev, KEY_RECORD, data[len - 18] & BIT(0)); > + } Thank you for the report, but this is quite ugly. I committed an alternative version of the fix. Thanks. -- Dmitry