On Thu, Aug 19, 2021 at 09:19:08AM -0700, Kees Cook wrote:
> On Thu, Aug 19, 2021 at 09:27:16AM -0300, Jason Gunthorpe wrote:
> > On Tue, Aug 17, 2021 at 11:05:26PM -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.
> > >
> > > Add struct_group() to mark region of struct mlx5_ib_mr that should be
> > > initialized to zero.
> > >
> > > Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> > > Cc: Doug Ledford <dledford@xxxxxxxxxx>
> > > Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> > > Cc: linux-rdma@xxxxxxxxxxxxxxx
> > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > > drivers/infiniband/hw/mlx5/mlx5_ib.h | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> > > index bf20a388eabe..f63bf204a7a1 100644
> > > +++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
> > > @@ -644,6 +644,7 @@ struct mlx5_ib_mr {
> > > struct ib_umem *umem;
> > >
> > > /* This is zero'd when the MR is allocated */
> > > + struct_group(cleared,
> > > union {
> > > /* Used only while the MR is in the cache */
> > > struct {
> > > @@ -691,12 +692,13 @@ struct mlx5_ib_mr {
> > > bool is_odp_implicit;
> > > };
> > > };
> > > + );
> > > };
> > >
> > > /* Zero the fields in the mr that are variant depending on usage */
> > > static inline void mlx5_clear_mr(struct mlx5_ib_mr *mr)
> > > {
> > > - memset(mr->out, 0, sizeof(*mr) - offsetof(struct mlx5_ib_mr, out));
> > > + memset(&mr->cleared, 0, sizeof(mr->cleared));
> > > }
> >
> > Why not use the memset_after(mr->umem) here?
>
> I can certainly do that instead. In this series I've tended to opt
> for groupings so the position of future struct member additions are
> explicitly chosen. (i.e. reducing the chance that a zeroing of the new
> member be a surprise.)
I saw the earlier RDMA patches where using other memset techniques
though? Were there flex arrays or something that made groups infeasible?
Jason
