* Andy Lutomirski [off-list ref] wrote:

On Tue, May 9, 2017 at 1:56 AM, Christoph Hellwig [off-list ref] wrote:

quoted

On Tue, May 09, 2017 at 08:45:22AM +0200, Ingo Molnar wrote:

quoted

We only have ~115 code blocks in the kernel that set/restore KERNEL_DS, it would
be a pity to add a runtime check to every system call ...

I think we should simply strive to remove all of them that aren't
in core scheduler / arch code.  Basically evetyytime we do the

        oldfs = get_fs();
        set_fs(KERNEL_DS);
        ..
        set_fs(oldfs);

trick we're doing something wrong, and there should always be better
ways to archive it.  E.g. using iov_iter with a ITER_KVEC type
consistently would already remove most of them.

How about trying to remove all of them?  If we could actually get rid
of all of them, we could drop the arch support, and we'd get faster,
simpler, shorter uaccess code throughout the kernel.

I'm all for that!

Thanks,

	Ingo