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net: ethernet: mtk_eth_soc: Avoid truncating allocation

PATCH Applied Kees Cook 3 participants 3 messages Jan 27, 2023 – Jan 31, 2023

Subsystems (4)
Networking Network drivers Arm MediaTek MediaTek Ethernet driver
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Kees Cook

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#0 lore raw

PATCH 1/1 net: ethernet: mtk_eth_soc: Avoid truncating allocation

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 <[email protected]>
Cc John Crispin <[email protected]>
Cc Sean Wang <[email protected]>
Cc Mark Lee <[email protected]>
Cc Lorenzo Bianconi <[email protected]>
Cc "David S. Miller" <[email protected]>
Cc Eric Dumazet <[email protected]>
Cc Jakub Kicinski <[email protected]>
Cc Paolo Abeni <[email protected]>
Cc Matthias Brugger <[email protected]>
Cc [email protected]
Cc [email protected]
Cc [email protected]
Signed-off-by Kees Cook <[email protected]>
---
 drivers/net/ethernet/mediatek/mtk_ppe.c | 3 +--
 drivers/net/ethernet/mediatek/mtk_ppe.h | 1 -
 2 files changed, 1 insertion(+), 3 deletions(-)
drivers/net/ethernet/mediatek/mtk_ppe.c +1 -2
index 451a87b1bc20..6883eb34cd8b 100644
@@ -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;
drivers/net/ethernet/mediatek/mtk_ppe.h +0 -1
index 16b02e1d4649..5e8bc48252b1 100644
@@ -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;
Signature · 1 line
2.34.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 11 lines · 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;
| ^~

...

Quoted 5 lines
Signed-off-by Kees Cook <[email protected]>
---
 drivers/net/ethernet/mediatek/mtk_ppe.c | 3 +--
 drivers/net/ethernet/mediatek/mtk_ppe.h | 1 -
 2 files changed, 1 insertion(+), 3 deletions(-)
Reviewed-by Simon Horman <[email protected]>
CI Applied
#2 lore raw
In reply to Kees Cook
This patch was applied to netdev/net.git (master) by Paolo Abeni <[email protected]>:

Hello:

This patch was applied to netdev/net.git (master)
by Paolo Abeni <[email protected]>:

Quoted 6 lines · On Fri, 27 Jan 2023 14:38:54 -0800 you wrote:

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:

Quoted 6 lines

../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;
| ^~

[...]

Here is the summary with links:
- net: ethernet: mtk_eth_soc: Avoid truncating allocation
https://git.kernel.org/netdev/net/c/f3eceaed9edd

You are awesome, thank you!

Signature · 2 lines
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