From: Kees Cook <keescook@chromium.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-kernel@vger.kernel.org, Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
linux-rdma@vger.kernel.org,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev,
linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org,
clang-built-linux@googlegroups.com,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 56/63] RDMA/mlx5: Use struct_group() to zero struct mlx5_ib_mr
Date: Thu, 19 Aug 2021 11:14:37 -0700 [thread overview]
Message-ID: <202108191106.1956C05A@keescook> (raw)
In-Reply-To: <20210819164757.GS543798@ziepe.ca>
On Thu, Aug 19, 2021 at 01:47:57PM -0300, Jason Gunthorpe wrote:
> 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@kernel.org>
> > > > Cc: Doug Ledford <dledford@redhat.com>
> > > > Cc: Jason Gunthorpe <jgg@ziepe.ca>
> > > > Cc: linux-rdma@vger.kernel.org
> > > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > > 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?
Which do you mean? When doing the conversions I tended to opt for
struct_group() since it provides more robust "intentionality". Strictly
speaking, the new memset helpers are doing field-spanning writes, but the
"clear to the end" pattern was so common it made sense to add the helpers,
as they're a bit less disruptive. It's totally up to you! :)
--
Kees Cook
next prev parent reply other threads:[~2021-08-19 18:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210818060533.3569517-1-keescook@chromium.org>
2021-08-18 6:04 ` [PATCH v2 02/63] net/mlx5e: Avoid field-overflowing memcpy() Kees Cook
2021-08-18 6:04 ` [PATCH v2 21/63] net/mlx5e: Use struct_group() for memcpy() region Kees Cook
2021-08-18 6:05 ` [PATCH v2 46/63] iw_cxgb4: Use memset_startat() for cpl_t5_pass_accept_rpl Kees Cook
2021-08-18 6:05 ` [PATCH v2 48/63] IB/mthca: Use memset_startat() for clearing mpt_entry Kees Cook
2021-08-18 6:05 ` [PATCH v2 56/63] RDMA/mlx5: Use struct_group() to zero struct mlx5_ib_mr Kees Cook
2021-08-19 12:27 ` Jason Gunthorpe
2021-08-19 16:19 ` Kees Cook
2021-08-19 16:47 ` Jason Gunthorpe
2021-08-19 18:14 ` Kees Cook [this message]
2021-08-20 12:34 ` Jason Gunthorpe
2021-08-20 15:56 ` Kees Cook
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