[PATCH 4.19 035/125] cec-api: prevent leaking memory through hole in structure

Greg Kroah-Hartman
2020-09-01T16:56:02Z

From: Hans Verkuil <hverkuil-cisco@xs4all.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@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/media/cec/cec-api.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/media/cec/cec-api.c b/drivers/media/cec/cec-api.c
index 4961573850d54..b2b3f779592fd 100644
--- a/drivers/media/cec/cec-api.c
+++ b/drivers/media/cec/cec-api.c
@@ -147,7 +147,13 @@ 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