linux-hardening - [PATCH AUTOSEL 6.6 14/22] enic: Avoid false positive under FORTIFY

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Date: Thu, 29 Feb 2024 15:39:07 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
	"David S . Miller" <davem@...emloft.net>,
	Sasha Levin <sashal@...nel.org>,
	benve@...co.com,
	satishkh@...co.com,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	netdev@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 14/22] enic: Avoid false positive under FORTIFY_SOURCE

From: Kees Cook <keescook@...omium.org>

[ Upstream commit 40b9385dd8e6a0515e1c9cd06a277483556b7286 ]

FORTIFY_SOURCE has been ignoring 0-sized destinations while the kernel
code base has been converted to flexible arrays. In order to enforce
the 0-sized destinations (e.g. with __counted_by), the remaining 0-sized
destinations need to be handled. Unfortunately, struct vic_provinfo
resists full conversion, as it contains a flexible array of flexible
arrays, which is only possible with the 0-sized fake flexible array.

Use unsafe_memcpy() to avoid future false positives under
CONFIG_FORTIFY_SOURCE.

Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/cisco/enic/vnic_vic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cisco/enic/vnic_vic.c b/drivers/net/ethernet/cisco/enic/vnic_vic.c
index 20fcb20b42ede..66b5778353389 100644
--- a/drivers/net/ethernet/cisco/enic/vnic_vic.c
+++ b/drivers/net/ethernet/cisco/enic/vnic_vic.c
@@ -49,7 +49,8 @@ int vic_provinfo_add_tlv(struct vic_provinfo *vp, u16 type, u16 length,
 
 	tlv->type = htons(type);
 	tlv->length = htons(length);
-	memcpy(tlv->value, value, length);
+	unsafe_memcpy(tlv->value, value, length,
+		      /* Flexible array of flexible arrays */);
 
 	vp->num_tlvs = htonl(ntohl(vp->num_tlvs) + 1);
 	vp->length = htonl(ntohl(vp->length) +
-- 
2.43.0