netdev - [PATCH] vmw_vsock: bypass false-positive Wnonnull warning with gcc-16

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Message-Id: <20260203163406.2636463-1-arnd@kernel.org>
Date: Tue,  3 Feb 2026 17:34:00 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Bryan Tan <bryan-bt.tan@...adcom.com>,
	Vishnu Dasa <vishnu.dasa@...adcom.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Simon Horman <horms@...nel.org>,
	HarshaVardhana S A <harshavardhana.sa@...adcom.com>,
	Bobby Eshleman <bobbyeshleman@...a.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux.dev,
	netdev@...r.kernel.org
Subject: [PATCH] vmw_vsock: bypass false-positive Wnonnull warning with gcc-16

From: Arnd Bergmann <arnd@...db.de>

The gcc-16.0.1 snapshot produces a false-positive warning that turns
into a build failure with CONFIG_WERROR:

In file included from arch/x86/include/asm/string.h:6,
                 from net/vmw_vsock/vmci_transport.c:10:
In function 'vmci_transport_packet_init',
    inlined from '__vmci_transport_send_control_pkt.constprop' at net/vmw_vsock/vmci_transport.c:198:2:
arch/x86/include/asm/string_32.h:150:25: error: argument 2 null where non-null expected because argument 3 is nonzero [-Werror=nonnull]
  150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~
net/vmw_vsock/vmci_transport.c:164:17: note: in expansion of macro 'memcpy'
  164 |                 memcpy(&pkt->u.wait, wait, sizeof(pkt->u.wait));
      |                 ^~~~~~
arch/x86/include/asm/string_32.h:150:25: note: in a call to built-in function '__builtin_memcpy'
net/vmw_vsock/vmci_transport.c:164:17: note: in expansion of macro 'memcpy'
  164 |                 memcpy(&pkt->u.wait, wait, sizeof(pkt->u.wait));
      |                 ^~~~~~

This seems relatively harmless, and it so far the only instance of this
warning I have found. The __vmci_transport_send_control_pkt function
is called either with wait=NULL or with one of the type values that
pass 'wait' into memcpy() here, but not from the same caller.

Replacing the memcpy with a struct assignment is otherwise the same
but avoids the warning.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 net/vmw_vsock/vmci_transport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
index 00f6bbdb035a..a64522be1bad 100644
--- a/net/vmw_vsock/vmci_transport.c
+++ b/net/vmw_vsock/vmci_transport.c
@@ -161,7 +161,7 @@ vmci_transport_packet_init(struct vmci_transport_packet *pkt,
 
 	case VMCI_TRANSPORT_PACKET_TYPE_WAITING_READ:
 	case VMCI_TRANSPORT_PACKET_TYPE_WAITING_WRITE:
-		memcpy(&pkt->u.wait, wait, sizeof(pkt->u.wait));
+		pkt->u.wait = *wait;
 		break;
 
 	case VMCI_TRANSPORT_PACKET_TYPE_REQUEST2:
-- 
2.39.5