[PATCH] media: cxusb: detect cxusb_ctrl_msg error in query

[Vito Caputo]

Don't use uninitialized ircode[] in cxusb_rc_query() when
cxusb_ctrl_msg() fails to populate its contents.

syzbot reported:

dvb-usb: bulk message failed: -22 (1/-30591)
=====================================================
BUG: KMSAN: uninit-value in ir_lookup_by_scancode drivers/media/rc/rc-main.c:494 [inline]
BUG: KMSAN: uninit-value in rc_g_keycode_from_table drivers/media/rc/rc-main.c:582 [inline]
BUG: KMSAN: uninit-value in rc_keydown+0x1a6/0x6f0 drivers/media/rc/rc-main.c:816
CPU: 1 PID: 11436 Comm: kworker/1:2 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events dvb_usb_read_remote_control
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x13a/0x2b0 mm/kmsan/kmsan_report.c:108
 __msan_warning+0x73/0xe0 mm/kmsan/kmsan_instr.c:250
 bsearch+0x1dd/0x250 lib/bsearch.c:41
 ir_lookup_by_scancode drivers/media/rc/rc-main.c:494 [inline]
 rc_g_keycode_from_table drivers/media/rc/rc-main.c:582 [inline]
 rc_keydown+0x1a6/0x6f0 drivers/media/rc/rc-main.c:816
 cxusb_rc_query+0x2e1/0x360 drivers/media/usb/dvb-usb/cxusb.c:548
 dvb_usb_read_remote_control+0xf9/0x290 drivers/media/usb/dvb-usb/dvb-usb-remote.c:261
 process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:256
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:150 [inline]
 kmsan_internal_chain_origin+0xd2/0x170 mm/kmsan/kmsan.c:314
 __msan_chain_origin+0x6b/0xe0 mm/kmsan/kmsan_instr.c:184
 rc_g_keycode_from_table drivers/media/rc/rc-main.c:583 [inline]
 rc_keydown+0x2c4/0x6f0 drivers/media/rc/rc-main.c:816
 cxusb_rc_query+0x2e1/0x360 drivers/media/usb/dvb-usb/cxusb.c:548
 dvb_usb_read_remote_control+0xf9/0x290 drivers/media/usb/dvb-usb/dvb-usb-remote.c:261
 process_one_work+0x1572/0x1ef0 kernel/workqueue.c:2269
 worker_thread+0x111b/0x2460 kernel/workqueue.c:2415
 kthread+0x4b5/0x4f0 kernel/kthread.c:256
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:355

Local variable description: ----ircode@cxusb_rc_query
Variable was created at:
 cxusb_rc_query+0x4d/0x360 drivers/media/usb/dvb-usb/cxusb.c:543
 dvb_usb_read_remote_control+0xf9/0x290 drivers/media/usb/dvb-usb/dvb-usb-remote.c:261

Signed-off-by: Vito Caputo <vcaputo@xxxxxxxxxxx>
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
---
 drivers/media/usb/dvb-usb/cxusb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb/cxusb.c b/drivers/media/usb/dvb-usb/cxusb.c
index f02fa0a67aa4..fac19ec46089 100644
--- a/drivers/media/usb/dvb-usb/cxusb.c
+++ b/drivers/media/usb/dvb-usb/cxusb.c
@@ -521,7 +521,8 @@ static int cxusb_rc_query(struct dvb_usb_device *d)
 {
 	u8 ircode[4];
 
-	cxusb_ctrl_msg(d, CMD_GET_IR_CODE, NULL, 0, ircode, 4);
+	if (cxusb_ctrl_msg(d, CMD_GET_IR_CODE, NULL, 0, ircode, 4) < 0)
+		return 0;
 
 	if (ircode[2] || ircode[3])
 		rc_keydown(d->rc_dev, RC_PROTO_NEC,
-- 
2.11.0