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Miller" , Jakub Kicinski , Cezary Rojewski , Pierre-Louis Bossart , Liam Girdwood , Jie Yang , Mark Brown Subject: [PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace Date: Mon, 4 Jan 2021 18:07:13 +0100 Message-Id: <20210104170713.66956-1-hdegoede@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Cc: alsa-devel@alsa-project.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, Ilan Peer , Hans de Goede X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" 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 Fixes: beee24695157 ("cfg80211: Save the regulatory domain when setting custom regulator") Signed-off-by: Hans de Goede --- 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); }