media: af9035: prevent buffer overflow on write

[ 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@kernel.org: 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@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/usb/dvb-usb-v2/af9035.c b/drivers/media/usb/dvb-usb-v2/af9035.c
index 666d319..1f6c1ee 100644 (file)
--- 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];