Re: [PATCH 47/64] btrfs: Use memset_after() to clear end of struct

On Sat, Jul 31, 2021 at 08:25:51AM -0700, Kees Cook wrote:

On Thu, Jul 29, 2021 at 12:33:37PM +0200, David Sterba wrote:

quoted

On Wed, Jul 28, 2021 at 02:56:31PM -0700, Kees Cook wrote:

quoted

On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote:

quoted

On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote:

quoted

 	}
 	if (need_reset) {
-		memset(&item->generation_v2, 0,
-			sizeof(*item) - offsetof(struct btrfs_root_item,
-					generation_v2));
-

Please add
		/* Clear all members from generation_v2 onwards */

quoted

+		memset_after(item, 0, level);

Perhaps there should be another helper memset_starting()? That would
make these cases a bit more self-documenting.

That would be better, yes.

quoted

+		memset_starting(item, 0, generation_v2);

memset_from?

For v2, I bikeshed this to "memset_startat" since "from" is semantically
close to "source" which I thought might be confusing. (I, too, did not
like "starting".) :)

memset_startat works for me, thanks.