linux-kernel - [PATCH 13/13] media: pulse8-cec: fix data timestamp at pulse8

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Message-ID: <8d5dfc87d297a92d5ccc750c5c002bbc4226d3ad.1729074076.git.mchehab+huawei@kernel.org>
Date: Wed, 16 Oct 2024 12:22:29 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: 
Cc: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	Hans Verkuil <hverkuil@...all.nl>,
	Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH 13/13] media: pulse8-cec: fix data timestamp at pulse8_setup()

There is a hidden overflow condition there. As date is signed
and u8 is unsigned, doing:

	date = (data[0] << 24)

With a value bigger than 07f will make all upper bits of date
0xffffffff. This can be demonstrated with this small code:

<code>

typedef int64_t time64_t;
typedef uint8_t u8;

int main(void)
{
	u8 data[] = { 0xde ,0xad , 0xbe, 0xef };
	time64_t date;

	date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
	printf("Invalid data = 0x%08lx\n", date);

	date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
	printf("Expected data = 0x%08lx\n", date);

	return 0;
}
</code>

Fix it by converting the upper bit calculation to unsigned.

Fixes: cea28e7a55e7 ("media: pulse8-cec: reorganize function order")
Cc: stable@...r.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
---
 drivers/media/cec/usb/pulse8/pulse8-cec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/cec/usb/pulse8/pulse8-cec.c b/drivers/media/cec/usb/pulse8/pulse8-cec.c
index ba67587bd43e..171366fe3544 100644
--- a/drivers/media/cec/usb/pulse8/pulse8-cec.c
+++ b/drivers/media/cec/usb/pulse8/pulse8-cec.c
@@ -685,7 +685,7 @@ static int pulse8_setup(struct pulse8 *pulse8, struct serio *serio,
 	err = pulse8_send_and_wait(pulse8, cmd, 1, cmd[0], 4);
 	if (err)
 		return err;
-	date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
+	date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
 	dev_info(pulse8->dev, "Firmware build date %ptT\n", &date);
 
 	dev_dbg(pulse8->dev, "Persistent config:\n");
-- 
2.47.0