[PATCH 3.10 054/103] brcmsmac: fix deadlock on missing firmware

Greg Kroah-Hartman
2014-06-04T23:34:46Z

From: Emil Goode <emilgoode@gmail.com>

commit 8fc1e8c240aab968db658b2d8d079b4391207a36 upstream.

When brcm80211 firmware is not installed networking hangs.
A deadlock happens because we call ieee80211_unregister_hw()
from the .start callback of struct ieee80211_ops. When .start
is called we are under rtnl lock and ieee80211_unregister_hw()
tries to take it again.

Function call stack:

dev_change_flags()
__dev_change_flags()
__dev_open()
ASSERT_RTNL() <-- Assert rtnl lock
ops->ndo_open()

.ndo_open = ieee80211_open,

ieee80211_open()
ieee80211_do_open()
drv_start()
local->ops->start()

.start = brcms_ops_start,

brcms_ops_start()
brcms_remove()
ieee80211_unregister_hw()
rtnl_lock() <-- Here we deadlock

Introduced by:
commit 25b5632fb35ca61b8ae3eee235edcdc2883f7a5e
("brcmsmac: request firmware in .start() callback")

This patch fixes the bug by removing the call to brcms_remove()
and moves the brcms_request_fw() call to the top of the .start
callback to not initiate anything unless firmware is installed.

Signed-off-by: Emil Goode <emilgoode@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

--- a/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
@@ -426,6 +426,12 @@ static int brcms_ops_start(struct ieee80
bool blocked;
int err;

+ if (!wl->ucode.bcm43xx_bomminor) {
+ err = brcms_request_fw(wl, wl->wlc->hw->d11core);
+ if (err)
+ return -ENOENT;
+ }
+
ieee80211_wake_queues(hw);
spin_lock_bh(&wl->lock);
blocked = brcms_rfkill_set_hw_state(wl);
@@ -433,14 +439,6 @@ static int brcms_ops_start(struct ieee80
if (!blocked)
wiphy_rfkill_stop_polling(wl->pub->ieee_hw->wiphy);

- if (!wl->ucode.bcm43xx_bomminor) {
- err = brcms_request_fw(wl, wl->wlc->hw->d11core);
- if (err) {
- brcms_remove(wl->wlc->hw->d11core);
- return -ENOENT;
- }
- }
-
spin_lock_bh(&wl->lock);
/* avoid acknowledging frames before a non-monitor device is added */
wl->mute_tx = true;