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