[PATCH v2] mac80211: Add attribute aligned(2) to struct 'action'

From: Mathieu Malaterre
Date: Thu Jan 24 2019 - 13:20:15 EST

During refactor in commit 9e478066eae4 ("mac80211: fix MU-MIMO
follow-MAC mode") a new struct 'action' was declared with packed
attribute as:

struct {
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
} __packed action;

But since struct 'ieee80211_hdr_3addr' is declared with an aligned
keyword as:

struct ieee80211_hdr {
__le16 frame_control;
__le16 duration_id;
u8 addr1[ETH_ALEN];
u8 addr2[ETH_ALEN];
u8 addr3[ETH_ALEN];
__le16 seq_ctrl;
u8 addr4[ETH_ALEN];
} __packed __aligned(2);

Solve the ambiguity of placing aligned structure in a packed one by
adding the aligned(2) attribute to struct 'action'. This seems to be the
behavior of gcc anyway, since the following is still compiling:

BUILD_BUG_ON(sizeof(action) != IEEE80211_MIN_ACTION_SIZE + 1);

This removes the following warning (W=1):

net/mac80211/rx.c:234:2: warning: alignment 1 of 'struct <anonymous>' is less than 2 [-Wpacked-not-aligned]

Cc: Johannes Berg <johannes.berg@xxxxxxxxx>
Suggested-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Mathieu Malaterre <malat@xxxxxxxxxx>
v2: It was suggested by Johannes that an arch actually need the pack attribute (alpha).

net/mac80211/rx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 45aad3d3108c..885df250b67e 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -231,7 +231,7 @@ static void ieee80211_handle_mu_mimo_mon(struct ieee80211_sub_if_data *sdata,
struct ieee80211_hdr_3addr hdr;
u8 category;
u8 action_code;
- } __packed action;
+ } __packed __aligned(2) action;

if (!sdata)