Re: [PATCH] soc: aspeed: fix a ternary sign expansion bug

Al Viro
2021-04-22T09:25:26Z

On Thu, Apr 22, 2021 at 12:11:44PM +0300, Dan Carpenter wrote:
> 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.

Hmm... Let's grep for kfifo_to_user() - smells like a possible recurring bug...
Yup -

samples/kfifo/bytestream-example.c:138: ret = kfifo_to_user(&test, buf, count, &copied);
samples/kfifo/inttype-example.c:131: ret = kfifo_to_user(&test, buf, count, &copied);
samples/kfifo/record-example.c:145: ret = kfifo_to_user(&test, buf, count, &copied);

All three are exactly like that one.