Commit 0ef049dc authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Johannes Berg
Browse files

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: default avatarArnd Bergmann <arnd@arndb.de>
Fixes: 98b62183 ("mac80211/cfg80211: add station events")
Fixes: 6f7a8d26 ("mac80211: send statistics with delete station event")
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 89f774e6

net/mac80211/sta_info.c

+16 −8
Original line number Diff line number Diff line
@@ -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);

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