linux-hardening - [PATCH 09/17] RDMA/mlx5: Use memset_after() to zero struct mlx5_ib

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Date:   Mon, 13 Dec 2021 14:33:23 -0800
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-rdma@...r.kernel.org,
        Leon Romanovsky <leonro@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 09/17] 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.

Cc: Doug Ledford <dledford@...hat.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: linux-rdma@...r.kernel.org
Acked-by: Leon Romanovsky <leonro@...dia.com>
Link: https://lore.kernel.org/lkml/YbByJSkBgLRp5S8V@unreal
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/infiniband/hw/mlx5/mlx5_ib.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index 4a7a56ed740b..ded10719b643 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -664,8 +664,8 @@ struct mlx5_ib_mr {
 
 	/* User MR data */
 	struct mlx5_cache_ent *cache_ent;
+	/* Everything after cache_ent is zero'd when MR allocated */
 
-	/* This is zero'd when the MR is allocated */
 	union {
 		/* Used only while the MR is in the cache */
 		struct {
@@ -718,7 +718,7 @@ 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, cache_ent);
 }
 
 static inline bool is_odp_mr(struct mlx5_ib_mr *mr)
-- 
2.30.2