[PATCH] [-next] net: marvell: prestera: Add explicit padding

* [PATCH] [-next] net: marvell: prestera: Add explicit padding
@ 2021-11-02  8:24 Geert Uytterhoeven
  2021-11-02  8:47 ` Arnd Bergmann
  2021-11-03  1:20 ` patchwork-bot+netdevbpf
  0 siblings, 2 replies; 5+ messages in thread
From: Geert Uytterhoeven @ 2021-11-02  8:24 UTC (permalink / raw)
  To: Taras Chornyi, David S . Miller, Jakub Kicinski,
	Volodymyr Mytnyk, Yevhen Orlov, Vadym Kochan
  Cc: Arnd Bergmann, netdev, linux-kernel, Geert Uytterhoeven

On m68k:

    In function ‘prestera_hw_build_tests’,
	inlined from ‘prestera_hw_switch_init’ at drivers/net/ethernet/marvell/prestera/prestera_hw.c:788:2:
    ././include/linux/compiler_types.h:335:38: error: call to ‘__compiletime_assert_345’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct prestera_msg_switch_attr_req) != 16
    ...

The driver assumes structure members are naturally aligned, but does not
add explicit padding, thus breaking architectures where integral values
are not always naturally aligned (e.g. on m68k, __alignof(int) is 2, not
4).

Fixes: bb5dbf2cc64d5cfa ("net: marvell: prestera: add firmware v4.0 support")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Compile-tested only.

BTW, I sincerely doubt the use of __packed on structs like:

    union prestera_msg_switch_param {
	    u8 mac[ETH_ALEN];
	    __le32 ageing_timeout_ms;
    } __packed;

This struct is only used as a member in another struct, where it is
be naturally aligned anyway.

Some of the other __packed attributes look fishy to me, too.
---
 drivers/net/ethernet/marvell/prestera/prestera_hw.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/net/ethernet/marvell/prestera/prestera_hw.c b/drivers/net/ethernet/marvell/prestera/prestera_hw.c
index 41ba17cb29657392..4f5f52dcdd9d2814 100644
--- a/drivers/net/ethernet/marvell/prestera/prestera_hw.c
+++ b/drivers/net/ethernet/marvell/prestera/prestera_hw.c
@@ -189,6 +189,7 @@ struct prestera_msg_switch_attr_req {
 	struct prestera_msg_cmd cmd;
 	__le32 attr;
 	union prestera_msg_switch_param param;
+	u8 pad[2];
 };
 
 struct prestera_msg_switch_init_resp {
@@ -313,6 +314,7 @@ struct prestera_msg_port_info_resp {
 	__le32 hw_id;
 	__le32 dev_id;
 	__le16 fp_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_vlan_req {
@@ -345,11 +347,13 @@ struct prestera_msg_bridge_req {
 	__le32 port;
 	__le32 dev;
 	__le16 bridge;
+	u8 pad[2];
 };
 
 struct prestera_msg_bridge_resp {
 	struct prestera_msg_ret ret;
 	__le16 bridge;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_action {
@@ -408,16 +412,19 @@ struct prestera_msg_acl_ruleset_bind_req {
 	__le32 port;
 	__le32 dev;
 	__le16 ruleset_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_ruleset_req {
 	struct prestera_msg_cmd cmd;
 	__le16 id;
+	u8 pad[2];
 };
 
 struct prestera_msg_acl_ruleset_resp {
 	struct prestera_msg_ret ret;
 	__le16 id;
+	u8 pad[2];
 };
 
 struct prestera_msg_span_req {
@@ -425,11 +432,13 @@ struct prestera_msg_span_req {
 	__le32 port;
 	__le32 dev;
 	u8 id;
+	u8 pad[3];
 };
 
 struct prestera_msg_span_resp {
 	struct prestera_msg_ret ret;
 	u8 id;
+	u8 pad[3];
 };
 
 struct prestera_msg_stp_req {
@@ -443,6 +452,7 @@ struct prestera_msg_stp_req {
 struct prestera_msg_rxtx_req {
 	struct prestera_msg_cmd cmd;
 	u8 use_sdma;
+	u8 pad[3];
 };
 
 struct prestera_msg_rxtx_resp {
@@ -455,12 +465,14 @@ struct prestera_msg_lag_req {
 	__le32 port;
 	__le32 dev;
 	__le16 lag_id;
+	u8 pad[2];
 };
 
 struct prestera_msg_cpu_code_counter_req {
 	struct prestera_msg_cmd cmd;
 	u8 counter_type;
 	u8 code;
+	u8 pad[2];
 };
 
 struct mvsw_msg_cpu_code_counter_ret {
-- 
2.25.1


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