mac80211: avoid excessive stack usage in sta_info

When CONFIG_OPTIMIZE_INLINING is set, the sta_info_insert_finish
function consumes more stack than normally, exceeding the
1024 byte limit on ARM:

net/mac80211/sta_info.c: In function 'sta_info_insert_finish':
net/mac80211/sta_info.c:561:1: error: the frame size of 1080 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

It turns out that there are two functions that put a 'struct station_info'
on the stack: __sta_info_destroy_part2 and sta_info_insert_finish, and
this structure alone requires up to 792 bytes.

Hoping that both are called rarely enough, this replaces the
on-stack structure with a dynamic allocation, which unfortunately
requires some suboptimal error handling for out-of-memory.

The __sta_info_destroy_part2 function is actually affected by the
stack usage twice because it calls cfg80211_del_sta_sinfo(), which
has another instance of struct station_info on its stack.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 98b6218388e3 ("mac80211/cfg80211: add station events")
Fixes: 6f7a8d26e266 ("mac80211: send statistics with delete station event")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 7e007cf12cb23d5903973a4d9c8dc2536d0a6515..b28e7a220d563429fb45518e7a8729fb97f619c3 100644 (file)
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -498,11 +498,17 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
 {
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
-       struct station_info sinfo;
+       struct station_info *sinfo;
        int err = 0;
 
        lockdep_assert_held(&local->sta_mtx);
 
+       sinfo = kzalloc(sizeof(struct station_info), GFP_KERNEL);
+       if (!sinfo) {
+               err = -ENOMEM;
+               goto out_err;
+       }
+
        /* check if STA exists already */
        if (sta_info_get_bss(sdata, sta->sta.addr)) {
                err = -EEXIST;
@@ -533,10 +539,9 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU)
        ieee80211_sta_debugfs_add(sta);
        rate_control_add_sta_debugfs(sta);
 
-       memset(&sinfo, 0, sizeof(sinfo));
-       sinfo.filled = 0;
-       sinfo.generation = local->sta_generation;
-       cfg80211_new_sta(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
+       sinfo->generation = local->sta_generation;
+       cfg80211_new_sta(sdata->dev, sta->sta.addr, sinfo, GFP_KERNEL);
+       kfree(sinfo);
 
        sta_dbg(sdata, "Inserted STA %pM\n", sta->sta.addr);
 
@@ -897,7 +902,7 @@ static void __sta_info_destroy_part2(struct sta_info *sta)
 {
        struct ieee80211_local *local = sta->local;
        struct ieee80211_sub_if_data *sdata = sta->sdata;
-       struct station_info sinfo = {};
+       struct station_info *sinfo;
        int ret;
 
        /*
@@ -935,8 +940,11 @@ static void __sta_info_destroy_part2(struct sta_info *sta)
 
        sta_dbg(sdata, "Removed STA %pM\n", sta->sta.addr);
 
-       sta_set_sinfo(sta, &sinfo);
-       cfg80211_del_sta_sinfo(sdata->dev, sta->sta.addr, &sinfo, GFP_KERNEL);
+       sinfo = kzalloc(sizeof(*sinfo), GFP_KERNEL);
+       if (sinfo)
+               sta_set_sinfo(sta, sinfo);
+       cfg80211_del_sta_sinfo(sdata->dev, sta->sta.addr, sinfo, GFP_KERNEL);
+       kfree(sinfo);
 
        rate_control_remove_sta_debugfs(sta);
        ieee80211_sta_debugfs_remove(sta);