[PATCH] media: pci: ttpci: av7110: avoid compiler optimization of reading data[0] in debiirq()

[Jia-Ju Bai]

In debiirq(), data_0 stores the value of data[0], but it can be dropped
by compiler optimization. Thus, data[0] is read through READ_ONCE().

Fixes: 6499a0db9b0f ("media: pci: ttpci: av7110: fix possible buffer overflow 
caused by bad DMA value in debiirq()")
Reported-by: Pavel Machek <pa...@ucw.cz>
Signed-off-by: Jia-Ju Bai <baiji...@tsinghua.edu.cn>
---
 drivers/media/pci/ttpci/av7110.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/pci/ttpci/av7110.c b/drivers/media/pci/ttpci/av7110.c
index bf36b1e22b63..f7d098d5b198 100644
--- a/drivers/media/pci/ttpci/av7110.c
+++ b/drivers/media/pci/ttpci/av7110.c
@@ -406,7 +406,7 @@ static void debiirq(unsigned long cookie)
        case DATA_CI_GET:
        {
                u8 *data = av7110->debi_virt;
-               u8 data_0 = data[0];
+               u8 data_0 = READ_ONCE(data[0]);
 
                if (data_0 < 2 && data[2] == 0xff) {
                        int flags = 0;
-- 
2.17.1