linux-kernel - [PATCH AUTOSEL 4.14 40/72] media: cec: silence shift wrapping warning in __cec_s_log

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Message-Id: <20200608232500.3369581-40-sashal@kernel.org>
Date:   Mon,  8 Jun 2020 19:24:28 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-media@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 40/72] media: cec: silence shift wrapping warning in __cec_s_log_addrs()

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit 3b5af3171e2d5a73ae6f04965ed653d039904eb6 ]

The log_addrs->log_addr_type[i] value is a u8 which is controlled by
the user and comes from the ioctl.  If it's over 31 then that results in
undefined behavior (shift wrapping) and that leads to a Smatch static
checker warning.  We already cap the value later so we can silence the
warning just by re-ordering the existing checks.

I think the UBSan checker will also catch this bug at runtime and
generate a warning.  But otherwise the bug is harmless.

Fixes: 9881fe0ca187 ("[media] cec: add HDMI CEC framework (adapter)")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/cec/cec-adap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/media/cec/cec-adap.c b/drivers/media/cec/cec-adap.c
index 0d7d687aeea0..061b7824f698 100644
--- a/drivers/media/cec/cec-adap.c
+++ b/drivers/media/cec/cec-adap.c
@@ -1624,6 +1624,10 @@ int __cec_s_log_addrs(struct cec_adapter *adap,
 		unsigned j;
 
 		log_addrs->log_addr[i] = CEC_LOG_ADDR_INVALID;
+		if (log_addrs->log_addr_type[i] > CEC_LOG_ADDR_TYPE_UNREGISTERED) {
+			dprintk(1, "unknown logical address type\n");
+			return -EINVAL;
+		}
 		if (type_mask & (1 << log_addrs->log_addr_type[i])) {
 			dprintk(1, "duplicate logical address type\n");
 			return -EINVAL;
@@ -1644,10 +1648,6 @@ int __cec_s_log_addrs(struct cec_adapter *adap,
 			dprintk(1, "invalid primary device type\n");
 			return -EINVAL;
 		}
-		if (log_addrs->log_addr_type[i] > CEC_LOG_ADDR_TYPE_UNREGISTERED) {
-			dprintk(1, "unknown logical address type\n");
-			return -EINVAL;
-		}
 		for (j = 0; j < feature_sz; j++) {
 			if ((features[j] & 0x80) == 0) {
 				if (op_is_dev_features)
-- 
2.25.1