Re: [patch v2] fcntl: return -EFAULT if copy_to_user fails

[Dan Carpenter <error27@gmail.com>]

On Thu, Jun 03, 2010 at 02:45:36PM +0200, Dan Carpenter wrote:
> The heuristic I use is that if we return a variable which is the 
> return value of copy_to_user() and it's non-zero then complain.  It 
> didn't find the f_getown_ex() because that return value could come from
> copy_to_user() or it could be -EINVAL.
> 
> I'll mess with it a bit and see if I can make it catch the f_getown_ex()
> bug.
> 

I changed the heuristic to complain if we return a non-zero return from
copy_to_user() and the minimum possible value of the return is not zero.

	ret = copy_to_user();
	if (ret)
		return ret;  // <- Complain.  The minimum value is 1.

Or:

	if (!foo)
		ret = -ENOMEM;
	if (!ret)
		ret = copy_to_user();
	return ret;  // <- Complain.  The minimum value is -ENOMEM.

This seems to work pretty well.  I've fixed all the bugs this found and 
I've pushed the check to the smatch repo.

regards,
dan carpenter