From: Dhyan K Prajapati <dhyan19022009@gmail.com>

When bringing up the wireless interface via virtual monitor mode,
iwlagn_bss_info_changed() can be called with a NULL bss_conf pointer
during ieee80211_add_virtual_monitor() -> ieee80211_do_open() sequence.

This causes a NULL pointer dereference when the function attempts to
access bss_conf fields at offset +0x10.

Crash signature:
  BUG: kernel NULL pointer dereference, address: 0000000000000000
  RIP: 0010:iwlagn_bss_info_changed+0x19d/0x640 [iwldvm]
  Call Trace:
   drv_link_info_changed+0x2b5/0x2c0 [mac80211]
   ieee80211_link_info_change_notify+0x13d/0x160 [mac80211]
   ieee80211_recalc_txpower+0x5c/0x60 [mac80211]
   ieee80211_assign_link_chanctx+0x182/0x410 [mac80211]
   ieee80211_add_virtual_monitor+0x17c/0x2b0 [mac80211]
   ieee80211_do_open+0x6d8/0x740 [mac80211]

Add an early NULL check for bss_conf before accessing its members.

Hardware: Dell Latitude E6430
WiFi: Intel Centrino Advanced-N 6205 [8086:0085]
Kernel: 6.18.7-061807-generic

Signed-off-by: Dhyan K Prajapati <dhyan19022009@gmail.com>
---
 drivers/net/wireless/intel/iwlwifi/dvm/rxon.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/wireless/intel/iwlwifi/dvm/rxon.c b/drivers/net/wireless/intel/iwlwifi/dvm/rxon.c
index e08e44cae..2d480b1d1 100644
--- a/drivers/net/wireless/intel/iwlwifi/dvm/rxon.c
+++ b/drivers/net/wireless/intel/iwlwifi/dvm/rxon.c
@@ -1392,6 +1392,11 @@ void iwlagn_bss_info_changed(struct ieee80211_hw *hw,
 
 	mutex_lock(&priv->mutex);
 
+	if (!bss_conf) {
+		mutex_unlock(&priv->mutex);
+		return;
+	}
+
 	if (changes & BSS_CHANGED_IDLE && vif->cfg.idle) {
 		/*
 		 * If we go idle, then clearly no "passive-no-rx"
-- 
2.43.0

On Wed, 2026-02-04 at 17:31 +0530, dhyaan19022009-hue wrote:
> From: Dhyan K Prajapati <dhyan19022009@gmail.com>
> 
> When bringing up the wireless interface via virtual monitor mode,
> iwlagn_bss_info_changed() can be called with a NULL bss_conf pointer
> during ieee80211_add_virtual_monitor() -> ieee80211_do_open() sequence.
> 
> This causes a NULL pointer dereference when the function attempts to
> access bss_conf fields at offset +0x10.
> 
> Crash signature:
>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>   RIP: 0010:iwlagn_bss_info_changed+0x19d/0x640 [iwldvm]
>   Call Trace:
>    drv_link_info_changed+0x2b5/0x2c0 [mac80211]
>    ieee80211_link_info_change_notify+0x13d/0x160 [mac80211]
>    ieee80211_recalc_txpower+0x5c/0x60 [mac80211]
>    ieee80211_assign_link_chanctx+0x182/0x410 [mac80211]
>    ieee80211_add_virtual_monitor+0x17c/0x2b0 [mac80211]
>    ieee80211_do_open+0x6d8/0x740 [mac80211]
> 
> Add an early NULL check for bss_conf before accessing its members.

If that really can happen, that'd be a mac80211 bug, not to be fixed in
a random driver. I see the crash above, but you've not even described it
correctly, it seems more likely to me that iwl_rxon_ctx_from_vif()
returned NULL.

johannes