media: pci: ttpci: av7110: fix possible buffer overflow caused by bad DMA value in...

media: pci: ttpci: av7110: fix possible buffer overflow caused by bad DMA value in debiirq()

The value av7110->debi_virt is stored in DMA memory, and it is assigned
to data, and thus data[0] can be modified at any time by malicious
hardware. In this case, "if (data[0] < 2)" can be passed, but then
data[0] can be changed into a large number, which may cause buffer
overflow when the code "av7110->ci_slot[data[0]]" is used.

To fix this possible bug, data[0] is assigned to a local variable, which
replaces the use of data[0].

Signed-off-by: Jia-Ju Bai <baijiaju@tsinghua.edu.cn>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>