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

Al Viro viro at zeniv.linux.org.uk
Thu Apr 22 19:24:59 AEST 2021

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.

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