wifi: ath11k: avoid deadlock during regulatory update in ath11k_regd_update()

Closes: #1023329

3 files changed, 104 insertions, 0 deletions

diff --git a/debian/changelog b/debian/changelog
index 0e56ead70..427facadc 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,10 @@
+linux (6.0.6-3) UNRELEASED; urgency=medium
+
+  * wifi: ath11k: avoid deadlock during regulatory update in
+    ath11k_regd_update() (Closes: #1023329)
+
+ -- Salvatore Bonaccorso <carnil@debian.org>  Thu, 03 Nov 2022 12:34:11 +0100
+
 linux (6.0.6-2) unstable; urgency=medium
 
   * Ignore ABI changes for ahci_fill_cmd_slot, phylink_create and
diff --git a/debian/patches/bugfix/all/wifi-ath11k-avoid-deadlock-during-regulatory-update-.patch b/debian/patches/bugfix/all/wifi-ath11k-avoid-deadlock-during-regulatory-update-.patch
new file mode 100644
index 000000000..b6ed4396d
--- /dev/null
+++ b/debian/patches/bugfix/all/wifi-ath11k-avoid-deadlock-during-regulatory-update-.patch
@@ -0,0 +1,96 @@
+From: Wen Gong <quic_wgong@quicinc.com>
+Date: Wed, 2 Nov 2022 13:48:03 +0200
+Subject: wifi: ath11k: avoid deadlock during regulatory update in
+ ath11k_regd_update()
+Origin: https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?id=f45cb6b29cd36514e13f7519770873d8c0457008
+Bug-Debian: https://bugs.debian.org/1023329
+
+(cherry picked from commit d99884ad9e3673a12879bc2830f6e5a66cccbd78 in ath-next
+as users are seeing this bug more now, also cc stable)
+
+Running this test in a loop it is easy to reproduce an rtnl deadlock:
+
+iw reg set FI
+ifconfig wlan0 down
+
+What happens is that thread A (workqueue) tries to update the regulatory:
+
+    try to acquire the rtnl_lock of ar->regd_update_work
+
+    rtnl_lock+0x17/0x20
+    ath11k_regd_update+0x15a/0x260 [ath11k]
+    ath11k_regd_update_work+0x15/0x20 [ath11k]
+    process_one_work+0x228/0x670
+    worker_thread+0x4d/0x440
+    kthread+0x16d/0x1b0
+    ret_from_fork+0x22/0x30
+
+And thread B (ifconfig) tries to stop the interface:
+
+    try to cancel_work_sync(&ar->regd_update_work) in ath11k_mac_op_stop().
+    ifconfig  3109 [003]  2414.232506: probe:
+
+    ath11k_mac_op_stop: (ffffffffc14187a0)
+    drv_stop+0x30 ([mac80211])
+    ieee80211_do_stop+0x5d2 ([mac80211])
+    ieee80211_stop+0x3e ([mac80211])
+    __dev_close_many+0x9e ([kernel.kallsyms])
+    __dev_change_flags+0xbe ([kernel.kallsyms])
+    dev_change_flags+0x23 ([kernel.kallsyms])
+    devinet_ioctl+0x5e3 ([kernel.kallsyms])
+    inet_ioctl+0x197 ([kernel.kallsyms])
+    sock_do_ioctl+0x4d ([kernel.kallsyms])
+    sock_ioctl+0x264 ([kernel.kallsyms])
+    __x64_sys_ioctl+0x92 ([kernel.kallsyms])
+    do_syscall_64+0x3a ([kernel.kallsyms])
+    entry_SYSCALL_64_after_hwframe+0x63 ([kernel.kallsyms])
+    __GI___ioctl+0x7 (/lib/x86_64-linux-gnu/libc-2.23.so)
+
+The sequence of deadlock is:
+
+1. Thread B calls rtnl_lock().
+
+2. Thread A starts to run and calls rtnl_lock() from within
+   ath11k_regd_update_work(), then enters wait state because the lock is owned by
+   thread B.
+
+3. Thread B continues to run and tries to call
+   cancel_work_sync(&ar->regd_update_work), but thread A is in
+   ath11k_regd_update_work() waiting for rtnl_lock(). So cancel_work_sync()
+   forever waits for ath11k_regd_update_work() to finish and we have a deadlock.
+
+Fix this by switching from using regulatory_set_wiphy_regd_sync() to
+regulatory_set_wiphy_regd(). Now cfg80211 will schedule another workqueue which
+handles the locking on it's own. So the ath11k workqueue can simply exit without
+taking any locks, avoiding the deadlock.
+
+Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3
+
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Wen Gong <quic_wgong@quicinc.com>
+[kvalo: improve commit log]
+Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
+---
+ drivers/net/wireless/ath/ath11k/reg.c | 6 +-----
+ 1 file changed, 1 insertion(+), 5 deletions(-)
+
+diff --git a/drivers/net/wireless/ath/ath11k/reg.c b/drivers/net/wireless/ath/ath11k/reg.c
+index 7ee3ff69dfc8..6fae4e61ede7 100644
+--- a/drivers/net/wireless/ath/ath11k/reg.c
++++ b/drivers/net/wireless/ath/ath11k/reg.c
+@@ -287,11 +287,7 @@ int ath11k_regd_update(struct ath11k *ar)
+ 		goto err;
+ 	}
+ 
+-	rtnl_lock();
+-	wiphy_lock(ar->hw->wiphy);
+-	ret = regulatory_set_wiphy_regd_sync(ar->hw->wiphy, regd_copy);
+-	wiphy_unlock(ar->hw->wiphy);
+-	rtnl_unlock();
++	ret = regulatory_set_wiphy_regd(ar->hw->wiphy, regd_copy);
+ 
+ 	kfree(regd_copy);
+ 
+-- 
+2.38.1
+
diff --git a/debian/patches/series b/debian/patches/series
index 0429a634a..d3ca53839 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -80,6 +80,7 @@ features/arm64/arm64-compat-Implement-misalignment-fixups-for-multi.patch
 # Miscellaneous bug fixes
 bugfix/all/disable-some-marvell-phys.patch
 bugfix/all/fs-add-module_softdep-declarations-for-hard-coded-cr.patch
+bugfix/all/wifi-ath11k-avoid-deadlock-during-regulatory-update-.patch
 
 # Miscellaneous features