[PATCH] net: ethernet: mtk_eth_soc: Avoid truncating allocation

[Kees Cook]

There doesn't appear to be a reason to truncate the allocation used for
flow_info, so do a full allocation and remove the unused empty struct.
GCC does not like having a reference to an object that has been
partially allocated, as bounds checking may become impossible when
such an object is passed to other code. Seen with GCC 13:

../drivers/net/ethernet/mediatek/mtk_ppe.c: In function 'mtk_foe_entry_commit_subflow':
../drivers/net/ethernet/mediatek/mtk_ppe.c:623:18: warning: array subscript 'struct mtk_flow_entry[0]' is partly outside array bounds of 'unsigned char[48]' [-Warray-bounds=]
  623 |         flow_info->l2_data.base_flow = entry;
      |                  ^~

Cc: Felix Fietkau <nbd@xxxxxxxx>
Cc: John Crispin <john@xxxxxxxxxxx>
Cc: Sean Wang <sean.wang@xxxxxxxxxxxx>
Cc: Mark Lee <Mark-MC.Lee@xxxxxxxxxxxx>
Cc: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-mediatek@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/net/ethernet/mediatek/mtk_ppe.c | 3 +--
 drivers/net/ethernet/mediatek/mtk_ppe.h | 1 -
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_ppe.c b/drivers/net/ethernet/mediatek/mtk_ppe.c
index 451a87b1bc20..6883eb34cd8b 100644
--- a/drivers/net/ethernet/mediatek/mtk_ppe.c
+++ b/drivers/net/ethernet/mediatek/mtk_ppe.c
@@ -615,8 +615,7 @@ mtk_foe_entry_commit_subflow(struct mtk_ppe *ppe, struct mtk_flow_entry *entry,
 	u32 ib1_mask = mtk_get_ib1_pkt_type_mask(ppe->eth) | MTK_FOE_IB1_UDP;
 	int type;
 
-	flow_info = kzalloc(offsetof(struct mtk_flow_entry, l2_data.end),
-			    GFP_ATOMIC);
+	flow_info = kzalloc(sizeof(*flow_info), GFP_ATOMIC);
 	if (!flow_info)
 		return;
 
diff --git a/drivers/net/ethernet/mediatek/mtk_ppe.h b/drivers/net/ethernet/mediatek/mtk_ppe.h
index 16b02e1d4649..5e8bc48252b1 100644
--- a/drivers/net/ethernet/mediatek/mtk_ppe.h
+++ b/drivers/net/ethernet/mediatek/mtk_ppe.h
@@ -279,7 +279,6 @@ struct mtk_flow_entry {
 		struct {
 			struct mtk_flow_entry *base_flow;
 			struct hlist_node list;
-			struct {} end;
 		} l2_data;
 	};
 	struct rhash_head node;
-- 
2.34.1