media: mceusb: Fix potential out-of-bounds shift

commit 1b43bad31fb0e00f45baf5b05bd21eb8d8ce7f58 upstream.

When processing a MCE_RSP_GETPORTSTATUS command, the bit index to set in
ir->txports_cabled comes from response data, and isn't validated.

As ir->txports_cabled is a u8, nothing should be done if the bit index
is greater than 7.

Cc: stable@vger.kernel.org
Reported-by: syzbot+ec3b3128c576e109171d@syzkaller.appspotmail.com
Signed-off-by: James Reynolds <jr@memlen.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/rc/mceusb.c b/drivers/media/rc/mceusb.c
index f1dbd05..c8d6367 100644 (file)
--- a/drivers/media/rc/mceusb.c
+++ b/drivers/media/rc/mceusb.c
@@ -1169,7 +1169,7 @@ static void mceusb_handle_command(struct mceusb_dev *ir, u8 *buf_in)
                switch (subcmd) {
                /* the one and only 5-byte return value command */
                case MCE_RSP_GETPORTSTATUS:
-                       if (buf_in[5] == 0)
+                       if (buf_in[5] == 0 && *hi < 8)
                                ir->txports_cabled |= 1 << *hi;
                        break;