[PATCH 01/11] media: dvb_ca_en50221: avoid speculation from CA slot

From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
To: unlisted-recipients:; (no To-header on input)
Cc: linuxarm@huawei.com, mauro.chehab@huawei.com,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org
Subject: [PATCH 01/11] media: dvb_ca_en50221: avoid speculation from CA slot
Date: Wed, 16 Jun 2021 14:28:27 +0200	[thread overview]
Message-ID: <77322db90902cd2c9d25fa3d614bf25809e9c609.1623846327.git.mchehab+huawei@kernel.org> (raw)
In-Reply-To: <cover.1623846327.git.mchehab+huawei@kernel.org>

As warned by smatch:
	drivers/media/dvb-core/dvb_ca_en50221.c:1392 dvb_ca_en50221_io_do_ioctl() warn: potential spectre issue 'ca->slot_info' [r] (local cap)

There's a potential of using a CAM ioctl for speculation.

The risk here is minimum, as only a small subset of DVB
boards have CI, with a CAM module installed. Also, exploiting
it would require an user capable of starting a DVB application.

There are probably a lot of easier ways to try to exploit.

Yet, it doesn't harm addressing it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 drivers/media/dvb-core/dvb_ca_en50221.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c
index b7e4a3371176..15a08d8c69ef 100644
--- a/drivers/media/dvb-core/dvb_ca_en50221.c
+++ b/drivers/media/dvb-core/dvb_ca_en50221.c
@@ -1386,6 +1386,7 @@ static int dvb_ca_en50221_io_do_ioctl(struct file *file,
 			err = -EINVAL;
 			goto out_unlock;
 		}
+		slot = array_index_nospec(slot, ca->slot_count);
 
 		info->type = CA_CI_LINK;
 		info->flags = 0;
-- 
2.31.1

