linux-hardening - [PATCH] RDMA/mlx5: Use memset_after() to zero struct mlx5_ib

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Message-Id: <20211118203138.1287134-1-keescook@chromium.org>
Date:   Thu, 18 Nov 2021 12:31:38 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] RDMA/mlx5: Use memset_after() to zero struct mlx5_ib_mr

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() to zero the end of struct mlx5_ib_mr that should
be initialized.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/infiniband/hw/mlx5/mlx5_ib.h | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index e636e954f6bf..af94c9fe8753 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -665,8 +665,7 @@ struct mlx5_ib_mr {
 	/* User MR data */
 	struct mlx5_cache_ent *cache_ent;
 	struct ib_umem *umem;
-
-	/* This is zero'd when the MR is allocated */
+	/* Everything after umem is zero'd when the MR is allocated */
 	union {
 		/* Used only while the MR is in the cache */
 		struct {
@@ -718,7 +717,7 @@ struct mlx5_ib_mr {
 /* 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_after(mr, 0, umem);
 }
 
 static inline bool is_odp_mr(struct mlx5_ib_mr *mr)
-- 
2.30.2