[PATCH] enic: Avoid false positive under FORTIFY_SOURCE

[Kees Cook]

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@xxxxxxxxxxxx>
---
Cc: Christian Benvenuti <benve@xxxxxxxxx>
Cc: Satish Kharat <satishkh@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
---
 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 20fcb20b42ed..66b577835338 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) +
-- 
2.34.1