netdev - [PATCH 44/64] iw_cxgb4: Use memset_after() for cpl_t5_pass_accept

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Message-Id: <20210727205855.411487-45-keescook@chromium.org>
Date:   Tue, 27 Jul 2021 13:58:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH 44/64] iw_cxgb4: Use memset_after() for cpl_t5_pass_accept_rpl

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() so memset() doesn't get confused about writing
beyond the destination member that is intended to be the starting point
of zeroing through the end of the struct. Additionally, since everything
appears to perform a roundup (including allocation), just change the
size of the struct itself and add a build-time check to validate the
expected size.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/infiniband/hw/cxgb4/cm.c            | 5 +++--
 drivers/net/ethernet/chelsio/cxgb4/t4_msg.h | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/hw/cxgb4/cm.c b/drivers/infiniband/hw/cxgb4/cm.c
index 291471d12197..7129ae025b2d 100644
--- a/drivers/infiniband/hw/cxgb4/cm.c
+++ b/drivers/infiniband/hw/cxgb4/cm.c
@@ -2471,7 +2471,8 @@ static int accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
 	skb_get(skb);
 	rpl = cplhdr(skb);
 	if (!is_t4(adapter_type)) {
-		skb_trim(skb, roundup(sizeof(*rpl5), 16));
+		BUILD_BUG_ON(sizeof(*rpl5) != roundup(sizeof(*rpl5), 16));
+		skb_trim(skb, sizeof(*rpl5));
 		rpl5 = (void *)rpl;
 		INIT_TP_WR(rpl5, ep->hwtid);
 	} else {
@@ -2487,7 +2488,7 @@ static int accept_cr(struct c4iw_ep *ep, struct sk_buff *skb,
 		opt2 |= CONG_CNTRL_V(CONG_ALG_TAHOE);
 		opt2 |= T5_ISS_F;
 		rpl5 = (void *)rpl;
-		memset(&rpl5->iss, 0, roundup(sizeof(*rpl5)-sizeof(*rpl), 16));
+		memset_after(rpl5, 0, opt0);
 		if (peer2peer)
 			isn += 4;
 		rpl5->iss = cpu_to_be32(isn);
diff --git a/drivers/net/ethernet/chelsio/cxgb4/t4_msg.h b/drivers/net/ethernet/chelsio/cxgb4/t4_msg.h
index fed5f93bf620..26433a62d7f0 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/t4_msg.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/t4_msg.h
@@ -497,7 +497,7 @@ struct cpl_t5_pass_accept_rpl {
 	__be32 opt2;
 	__be64 opt0;
 	__be32 iss;
-	__be32 rsvd;
+	__be32 rsvd[3];
 };
 
 struct cpl_act_open_req {
-- 
2.30.2