[PATCH AUTOSEL 4.14 01/32] media: af9035: prevent buffer overflow on write

[Sasha Levin]

From: Jozef Balga <jozef.balga@xxxxxxxxx>

[ Upstream commit 312f73b648626a0526a3aceebb0a3192aaba05ce ]

When less than 3 bytes are written to the device, memcpy is called with
negative array size which leads to buffer overflow and kernel panic. This
patch adds a condition and returns -EOPNOTSUPP instead.
Fixes bugzilla issue 64871

[mchehab+samsung@xxxxxxxxxx: fix a merge conflict and changed the
 condition to match the patch's comment, e. g. len == 3 could
 also be valid]
Signed-off-by: Jozef Balga <jozef.balga@xxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
 drivers/media/usb/dvb-usb-v2/af9035.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 666d319d3d1a..1f6c1eefe389 100644
--- a/drivers/media/usb/dvb-usb-v2/af9035.c
+++ b/drivers/media/usb/dvb-usb-v2/af9035.c
@@ -402,8 +402,10 @@ static int af9035_i2c_master_xfer(struct i2c_adapter *adap,
 			if (msg[0].addr == state->af9033_i2c_addr[1])
 				reg |= 0x100000;
 
-			ret = af9035_wr_regs(d, reg, &msg[0].buf[3],
-					msg[0].len - 3);
+			ret = (msg[0].len >= 3) ? af9035_wr_regs(d, reg,
+							         &msg[0].buf[3],
+							         msg[0].len - 3)
+					        : -EOPNOTSUPP;
 		} else {
 			/* I2C write */
 			u8 buf[MAX_XFER_SIZE];
-- 
2.17.1