Messages in this thread | | | Date | Wed, 28 Jul 2021 14:56:31 -0700 | From | Kees Cook <> | Subject | Re: [PATCH 47/64] btrfs: Use memset_after() to clear end of struct |
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On Wed, Jul 28, 2021 at 11:42:15AM +0200, David Sterba wrote: > On Tue, Jul 27, 2021 at 01:58:38PM -0700, Kees Cook wrote: > > In preparation for FORTIFY_SOURCE performing compile-time and run-time > > field bounds checking for memset(), avoid intentionally writing across > > neighboring fields. > > > > Use memset_after() so memset() doesn't get confused about writing > > beyond the destination member that is intended to be the starting point > > of zeroing through the end of the struct. > > > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > fs/btrfs/root-tree.c | 5 +---- > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c > > index 702dc5441f03..ec9e78f65fca 100644 > > --- a/fs/btrfs/root-tree.c > > +++ b/fs/btrfs/root-tree.c > > @@ -39,10 +39,7 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot, > > need_reset = 1; > > } > > 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 */ > > > + memset_after(item, 0, level);
Perhaps there should be another helper memset_starting()? That would make these cases a bit more self-documenting.
+ memset_starting(item, 0, generation_v2);
> > generate_random_guid(item->uuid); > > Acked-by: David Sterba <dsterba@suse.com>
What do you think?
-Kees
-- Kees Cook
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