[PATCH for-next 06/25] bnxt_en: Use struct_group_attr() for memcpy() region

From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
	Michael Chan <michael.chan@broadcom.com>,
	"Gustavo A . R . Silva" <gustavoars@kernel.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Daniel Micay <danielmicay@gmail.com>,
	Francis Laniel <laniel_francis@privacyrequired.com>,
	Bart Van Assche <bvanassche@acm.org>,
	David Gow <davidgow@google.com>,
	linux-mm@kvack.org, clang-built-linux@googlegroups.com,
	linux-hardening@vger.kernel.org
Subject: [PATCH for-next 06/25] bnxt_en: Use struct_group_attr() for memcpy() region
Date: Sun, 22 Aug 2021 00:51:03 -0700	[thread overview]
Message-ID: <20210822075122.864511-7-keescook@chromium.org> (raw)
In-Reply-To: <20210822075122.864511-1-keescook@chromium.org>

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally writing across neighboring fields.

Use struct_group() around members queue_id, min_bw, max_bw, tsa, pri_lvl,
and bw_weight so they can be referenced together. This will allow memcpy()
and sizeof() to more easily reason about sizes, improve readability,
and avoid future warnings about writing beyond the end of queue_id.

"pahole" shows no size nor member offset changes to struct bnxt_cos2bw_cfg.
"objdump -d" shows no meaningful object code changes (i.e. only source
line number induced differences and optimizations).

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/lkml/CACKFLinDc6Y+P8eZ=450yA1nMC7swTURLtcdyiNR=9J6dfFyBg@mail.gmail.com
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/lkml/20210728044517.GE35706@embeddedor
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c |  4 ++--
 drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.h | 14 ++++++++------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
index 8e90224c43a2..2ddebbfc9cc9 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.c
@@ -148,10 +148,10 @@ static int bnxt_hwrm_queue_cos2bw_qcfg(struct bnxt *bp, struct ieee_ets *ets)
 	}
 
 	data = &resp->queue_id0 + offsetof(struct bnxt_cos2bw_cfg, queue_id);
-	for (i = 0; i < bp->max_tc; i++, data += sizeof(cos2bw) - 4) {
+	for (i = 0; i < bp->max_tc; i++, data += sizeof(cos2bw.cfg)) {
 		int tc;
 
-		memcpy(&cos2bw.queue_id, data, sizeof(cos2bw) - 4);
+		memcpy(&cos2bw.cfg, data, sizeof(cos2bw.cfg));
 		if (i == 0)
 			cos2bw.queue_id = resp->queue_id0;
 
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.h
index 6eed231de565..716742522161 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_dcb.h
@@ -23,13 +23,15 @@ struct bnxt_dcb {
 
 struct bnxt_cos2bw_cfg {
 	u8			pad[3];
-	u8			queue_id;
-	__le32			min_bw;
-	__le32			max_bw;
+	struct_group_attr(cfg, __packed,
+		u8		queue_id;
+		__le32		min_bw;
+		__le32		max_bw;
 #define BW_VALUE_UNIT_PERCENT1_100		(0x1UL << 29)
-	u8			tsa;
-	u8			pri_lvl;
-	u8			bw_weight;
+		u8		tsa;
+		u8		pri_lvl;
+		u8		bw_weight;
+	);
 	u8			unused;
 };
 
-- 
2.30.2

