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

Al Viro
2021-04-22T09:26:46Z

On Thu, Apr 22, 2021 at 09:24:59AM +0000, Al Viro wrote:
> 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.

Nevermind, you've already caught and posted that bunch. Sorry for noise...