Subject: Confused about usercopy_64.c

From: Timur Tabi <[email-masked]>
Date: Mon, 10 Mar 2008 11:38:49 -0500

I'm confused about something in usercopy_64.c:

unsigned long copy_from_user(void *to, const void __user *from, unsigned long n)
{
	if (likely(access_ok(VERIFY_READ, from, n)))
		n = __copy_from_user(to, from, n);
	else
		memset(to, 0, n);
	return n;
}

If access_ok() returns false, then that means that we cannot copy the data from
user-space.  So why are we returning 'n'?  Shouldn't we return zero, to let the
caller know that the function failed?

-- 
Timur Tabi
Linux kernel developer at Freescale