David Laight [off-list ref] writes:

From: Dan Carpenter

quoted

Sent: 22 April 2021 10:12

The intent here was to return negative error codes but it actually
returns positive values.  The problem is that type promotion with
ternary operations is quite complicated.

"ret" is an int.  "copied" is a u32.  And the snoop_file_read() function
returns long.  What happens is that "ret" is cast to u32 and becomes
positive then it's cast to long and it's still positive.

Fix this by removing the ternary so that "ret" is type promoted directly
to long.

Fixes: 3772e5da4454 ("drivers/misc: Aspeed LPC snoop output using misc chardev")
Signed-off-by: Dan Carpenter <redacted>
---
 drivers/soc/aspeed/aspeed-lpc-snoop.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/soc/aspeed/aspeed-lpc-snoop.c b/drivers/soc/aspeed/aspeed-lpc-snoop.c
index 210455efb321..eceeaf8dfbeb 100644
--- a/drivers/soc/aspeed/aspeed-lpc-snoop.c
+++ b/drivers/soc/aspeed/aspeed-lpc-snoop.c

@@ -94,8 +94,10 @@ static ssize_t snoop_file_read(struct file *file, char __user *buffer,
 			return -EINTR;
 	}
 	ret = kfifo_to_user(&chan->fifo, buffer, count, &copied);
+	if (ret)
+		return ret;

-	return ret ? ret : copied;
+	return copied;

I wonder if changing it to:
	return ret ? ret + 0L : copied;

Might make people think in the future and not convert it back
as an 'optimisation'.

It rather made me think: "what the heck is going on here?!"

Shouldn't it better be:

 	return ret ? ret : (long)copied;

or even:

        return ret ?: (long)copied;

?

-- Sergey Organov