[PATCH 4.5 088/124] mac80211: avoid excessive stack usage in sta_info

From: Greg Kroah-Hartman
Date: Sun Apr 17 2016 - 22:35:55 EST


4.5-stable review patch. If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@xxxxxxxx>

commit 0ef049dc1167fe834d0ad5d63f89eddc5c70f6e4 upstream.

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@xxxxxxxx>
Fixes: 98b6218388e3 ("mac80211/cfg80211: add station events")
Fixes: 6f7a8d26e266 ("mac80211: send statistics with delete station event")
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
net/mac80211/sta_info.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)

--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -498,11 +498,17 @@ static int sta_info_insert_finish(struct
{
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;
@@ -536,10 +542,9 @@ static int sta_info_insert_finish(struct
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);

@@ -901,7 +906,7 @@ static void __sta_info_destroy_part2(str
{
struct ieee80211_local *local = sta->local;
struct ieee80211_sub_if_data *sdata = sta->sdata;
- struct station_info sinfo = {};
+ struct station_info *sinfo;
int ret;

/*
@@ -939,8 +944,11 @@ static void __sta_info_destroy_part2(str

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);