linux-kernel - [PATCH AUTOSEL 4.9 19/26] cec-api: prevent leaking memory through hole in structure

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Message-Id: <20200821161938.349246-19-sashal@kernel.org>
Date:   Fri, 21 Aug 2020 12:19:30 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: [PATCH AUTOSEL 4.9 19/26] cec-api: prevent leaking memory through hole in structure

From: Hans Verkuil <hverkuil-cisco@...all.nl>

[ Upstream commit 6c42227c3467549ddc65efe99c869021d2f4a570 ]

Fix this smatch warning:

drivers/media/cec/core/cec-api.c:156 cec_adap_g_log_addrs() warn: check that 'log_addrs' doesn't leak information (struct has a hole after
'features')

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/staging/media/cec/cec-api.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/cec/cec-api.c b/drivers/staging/media/cec/cec-api.c
index e274e2f223986..264bb7d1efcb8 100644
--- a/drivers/staging/media/cec/cec-api.c
+++ b/drivers/staging/media/cec/cec-api.c
@@ -141,7 +141,13 @@ static long cec_adap_g_log_addrs(struct cec_adapter *adap,
 	struct cec_log_addrs log_addrs;
 
 	mutex_lock(&adap->lock);
-	log_addrs = adap->log_addrs;
+	/*
+	 * We use memcpy here instead of assignment since there is a
+	 * hole at the end of struct cec_log_addrs that an assignment
+	 * might ignore. So when we do copy_to_user() we could leak
+	 * one byte of memory.
+	 */
+	memcpy(&log_addrs, &adap->log_addrs, sizeof(log_addrs));
 	if (!adap->is_configured)
 		memset(log_addrs.log_addr, CEC_LOG_ADDR_INVALID,
 		       sizeof(log_addrs.log_addr));
-- 
2.25.1