[PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace
From: Hans de Goede <hidden>
Date: 2021-01-04 17:09:06
Commit beee24695157 ("cfg80211: Save the regulatory domain when
setting custom regulatory") adds a get_wiphy_regdom call to
wiphy_apply_custom_regulatory. But as the comment above
wiphy_apply_custom_regulatory says:
"/* Used by drivers prior to wiphy registration */"
this function is used by driver's probe function before the wiphy is
registered and at this point wiphy->regd will typically by NULL and
calling rcu_dereference_rtnl on a NULL pointer causes the following
warning/backtrace:
=============================
WARNING: suspicious RCU usage
5.11.0-rc1+ #19 Tainted: G W
-----------------------------
net/wireless/reg.c:144 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
2 locks held by kworker/2:0/22:
#0: ffff9a4bc104df38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1ee/0x570
#1: ffffb6e94010be78 ((work_completion)(&fw_work->work)){+.+.}-{0:0}, at: process_one_work+0x1ee/0x570
stack backtrace:
CPU: 2 PID: 22 Comm: kworker/2:0 Tainted: G W 5.11.0-rc1+ #19
Hardware name: LENOVO 60073/INVALID, BIOS 01WT17WW 08/01/2014
Workqueue: events request_firmware_work_func
Call Trace:
dump_stack+0x8b/0xb0
get_wiphy_regdom+0x57/0x60 [cfg80211]
wiphy_apply_custom_regulatory+0xa0/0xf0 [cfg80211]
brcmf_cfg80211_attach+0xb02/0x1360 [brcmfmac]
brcmf_attach+0x189/0x460 [brcmfmac]
brcmf_sdio_firmware_callback+0x78a/0x8f0 [brcmfmac]
brcmf_fw_request_done+0x67/0xf0 [brcmfmac]
request_firmware_work_func+0x3d/0x70
process_one_work+0x26e/0x570
worker_thread+0x55/0x3c0
? process_one_work+0x570/0x570
kthread+0x137/0x150
? __kthread_bind_mask+0x60/0x60
ret_from_fork+0x22/0x30
Add a check for wiphy->regd being NULL before calling get_wiphy_regdom
(as is already done in other places) to fix this.
wiphy->regd will likely always be NULL when wiphy_apply_custom_regulatory
gets called, so arguably the tmp = get_wiphy_regdom() and
rcu_free_regdom(tmp) calls should simply be dropped, this patch keeps the
2 calls, to allow drivers to call wiphy_apply_custom_regulatory more then
once if necessary.
Cc: Ilan Peer <redacted>
Fixes: beee24695157 ("cfg80211: Save the regulatory domain when setting custom regulator")
Signed-off-by: Hans de Goede <redacted>
---
net/wireless/reg.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index bb72447ad960..9254b9cbaa21 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c@@ -2547,7 +2547,7 @@ static void handle_band_custom(struct wiphy *wiphy, void wiphy_apply_custom_regulatory(struct wiphy *wiphy, const struct ieee80211_regdomain *regd) { - const struct ieee80211_regdomain *new_regd, *tmp; + const struct ieee80211_regdomain *new_regd, *tmp = NULL; enum nl80211_band band; unsigned int bands_set = 0;
@@ -2571,7 +2571,8 @@ void wiphy_apply_custom_regulatory(struct wiphy *wiphy, if (IS_ERR(new_regd)) return; - tmp = get_wiphy_regdom(wiphy); + if (wiphy->regd) + tmp = get_wiphy_regdom(wiphy); rcu_assign_pointer(wiphy->regd, new_regd); rcu_free_regdom(tmp); }
--
2.28.0