[PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[Hans de Goede]

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 <ilan.peer@intel.com>
Fixes: beee24695157 ("cfg80211: Save the regulatory domain when setting custom regulator")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 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

RE: [PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[Peer, Ilan]

Hi,

> -----Original Message-----
> From: Hans de Goede <hdegoede@redhat.com>
> Sent: Monday, January 04, 2021 19:07
> To: Johannes Berg <johannes@sipsolutions.net>; David S . Miller
> <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Rojewski,
> Cezary <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
> louis.bossart@linux.intel.com>; Liam Girdwood
> <liam.r.girdwood@linux.intel.com>; Jie Yang <yang.jie@linux.intel.com>;
> Mark Brown <broonie@kernel.org>
> Cc: Hans de Goede <hdegoede@redhat.com>; linux-
> wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; alsa-devel@alsa-project.org; Peer, Ilan
> <ilan.peer@intel.com>
> Subject: [PATCH] cfg80211: Fix "suspicious RCU usage in
> wiphy_apply_custom_regulatory" warning/backtrace
> 
> 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->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 <ilan.peer@intel.com>
> Fixes: beee24695157 ("cfg80211: Save the regulatory domain when setting
> custom regulator")
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  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);

This only fixes the first case where the pointer in NULL and does not handle the wrong RCU usage in other cases.

I'll prepare a fix for this.

Thanks for addressing the bug,

Ilan.

Re: [PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[Hans de Goede]

Hi,

On 1/5/21 10:24 AM, Peer, Ilan wrote:
> Hi,
> 
>> -----Original Message-----
>> From: Hans de Goede <hdegoede@redhat.com>
>> Sent: Monday, January 04, 2021 19:07
>> To: Johannes Berg <johannes@sipsolutions.net>; David S . Miller
>> <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Rojewski,
>> Cezary <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
>> louis.bossart@linux.intel.com>; Liam Girdwood
>> <liam.r.girdwood@linux.intel.com>; Jie Yang <yang.jie@linux.intel.com>;
>> Mark Brown <broonie@kernel.org>
>> Cc: Hans de Goede <hdegoede@redhat.com>; linux-
>> wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
>> kernel@vger.kernel.org; alsa-devel@alsa-project.org; Peer, Ilan
>> <ilan.peer@intel.com>
>> Subject: [PATCH] cfg80211: Fix "suspicious RCU usage in
>> wiphy_apply_custom_regulatory" warning/backtrace
>>
>> 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->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 <ilan.peer@intel.com>
>> Fixes: beee24695157 ("cfg80211: Save the regulatory domain when setting
>> custom regulator")
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  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);
> 
> This only fixes the first case where the pointer in NULL and does not handle the wrong RCU usage in other cases.
> 
> I'll prepare a fix for this.

Any luck with this? This is a regression in 5.11, so this really should
be fixed in a future 5.11-rc and the clock is running out.

Regards,

Hans

RE: [PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[Peer, Ilan]

> -----Original Message-----
> From: Hans de Goede <hdegoede@redhat.com>
> Sent: Monday, January 18, 2021 23:09
> To: Peer, Ilan <ilan.peer@intel.com>; Johannes Berg
> <johannes@sipsolutions.net>; David S . Miller <davem@davemloft.net>;
> Jakub Kicinski <kuba@kernel.org>; Rojewski, Cezary
> <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
> louis.bossart@linux.intel.com>; Liam Girdwood
> <liam.r.girdwood@linux.intel.com>; Jie Yang <yang.jie@linux.intel.com>;
> Mark Brown <broonie@kernel.org>
> Cc: linux-wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; alsa-devel@alsa-project.org
> Subject: Re: [PATCH] cfg80211: Fix "suspicious RCU usage in
> wiphy_apply_custom_regulatory" warning/backtrace
> 
> Hi,
> 
> On 1/5/21 10:24 AM, Peer, Ilan wrote:
> > Hi,
> >
> >> -----Original Message-----
> >> From: Hans de Goede <hdegoede@redhat.com>
> >> Sent: Monday, January 04, 2021 19:07
> >> To: Johannes Berg <johannes@sipsolutions.net>; David S . Miller
> >> <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Rojewski,
> >> Cezary <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
> >> louis.bossart@linux.intel.com>; Liam Girdwood
> >> <liam.r.girdwood@linux.intel.com>; Jie Yang
> >> <yang.jie@linux.intel.com>; Mark Brown <broonie@kernel.org>
> >> Cc: Hans de Goede <hdegoede@redhat.com>; linux-
> >> wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
> >> kernel@vger.kernel.org; alsa-devel@alsa-project.org; Peer, Ilan
> >> <ilan.peer@intel.com>
> >> Subject: [PATCH] cfg80211: Fix "suspicious RCU usage in
> >> wiphy_apply_custom_regulatory" warning/backtrace
> >>
> >> 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->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 <ilan.peer@intel.com>
> >> Fixes: beee24695157 ("cfg80211: Save the regulatory domain when
> >> setting custom regulator")
> >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> >> ---
> >>  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);
> >
> > This only fixes the first case where the pointer in NULL and does not handle
> the wrong RCU usage in other cases.
> >
> > I'll prepare a fix for this.
> 
> Any luck with this? This is a regression in 5.11, so this really should be fixed in
> a future 5.11-rc and the clock is running out.
> 

Yes. The fix is ready. We'll send it.

Regards,

Ilan.

RE: [PATCH] cfg80211: Fix "suspicious RCU usage in wiphy_apply_custom_regulatory" warning/backtrace

[Peer, Ilan]

Hi,

This fix can be found here. It was merged to the mac80211 tree.

https://patchwork.kernel.org/project/linux-wireless/patch/iwlwifi.20210105165657.613e9a876829.Ia38d27dbebea28bf9c56d70691d243186ede70e7@changeid/

Regards,

Ilan.

> -----Original Message-----
> From: Hans de Goede <hdegoede@redhat.com>
> Sent: Monday, January 18, 2021 23:09
> To: Peer, Ilan <ilan.peer@intel.com>; Johannes Berg
> <johannes@sipsolutions.net>; David S . Miller <davem@davemloft.net>;
> Jakub Kicinski <kuba@kernel.org>; Rojewski, Cezary
> <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
> louis.bossart@linux.intel.com>; Liam Girdwood
> <liam.r.girdwood@linux.intel.com>; Jie Yang <yang.jie@linux.intel.com>;
> Mark Brown <broonie@kernel.org>
> Cc: linux-wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; alsa-devel@alsa-project.org
> Subject: Re: [PATCH] cfg80211: Fix "suspicious RCU usage in
> wiphy_apply_custom_regulatory" warning/backtrace
> 
> Hi,
> 
> On 1/5/21 10:24 AM, Peer, Ilan wrote:
> > Hi,
> >
> >> -----Original Message-----
> >> From: Hans de Goede <hdegoede@redhat.com>
> >> Sent: Monday, January 04, 2021 19:07
> >> To: Johannes Berg <johannes@sipsolutions.net>; David S . Miller
> >> <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Rojewski,
> >> Cezary <cezary.rojewski@intel.com>; Pierre-Louis Bossart <pierre-
> >> louis.bossart@linux.intel.com>; Liam Girdwood
> >> <liam.r.girdwood@linux.intel.com>; Jie Yang
> >> <yang.jie@linux.intel.com>; Mark Brown <broonie@kernel.org>
> >> Cc: Hans de Goede <hdegoede@redhat.com>; linux-
> >> wireless@vger.kernel.org; netdev@vger.kernel.org; linux-
> >> kernel@vger.kernel.org; alsa-devel@alsa-project.org; Peer, Ilan
> >> <ilan.peer@intel.com>
> >> Subject: [PATCH] cfg80211: Fix "suspicious RCU usage in
> >> wiphy_apply_custom_regulatory" warning/backtrace
> >>
> >> 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->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 <ilan.peer@intel.com>
> >> Fixes: beee24695157 ("cfg80211: Save the regulatory domain when
> >> setting custom regulator")
> >> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> >> ---
> >>  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);
> >
> > This only fixes the first case where the pointer in NULL and does not handle
> the wrong RCU usage in other cases.
> >
> > I'll prepare a fix for this.
> 
> Any luck with this? This is a regression in 5.11, so this really should be fixed in
> a future 5.11-rc and the clock is running out.
> 
> Regards,
> 
> Hans