linux-kernel - [PATCH] iwlwifi: mvm: Fix potential NULL dereference for sta

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Message-Id: <20220121111418.9144-1-tiwai@suse.de>
Date:   Fri, 21 Jan 2022 12:14:18 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Luca Coelho <luciano.coelho@...el.com>
Cc:     Johannes Berg <johannes.berg@...el.com>,
        Oliver Neukum <oneukum@...e.de>,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iwlwifi: mvm: Fix potential NULL dereference for sta

The recent fix for NULL sta in iwl_mvm_get_tx_rate() may still hit a
potential NULL dereference, as iwl_mvm_sta_from_mac80211() is called
unconditionally (although this doesn't seem happening, practically
seen, thanks to the compiler optimization).

This patch addresses it by dropping the temporary variable.

Fixes: d599f714b73e ("iwlwifi: mvm: don't crash on invalid rate w/o STA")
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/net/wireless/intel/iwlwifi/mvm/tx.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
index 6fa2c12f7955..4d1ddca73fb0 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
@@ -318,15 +318,14 @@ static u32 iwl_mvm_get_tx_rate(struct iwl_mvm *mvm,
 
 	/* info->control is only relevant for non HW rate control */
 	if (!ieee80211_hw_check(mvm->hw, HAS_RATE_CONTROL)) {
-		struct iwl_mvm_sta *mvmsta = iwl_mvm_sta_from_mac80211(sta);
-
 		/* HT rate doesn't make sense for a non data frame */
 		WARN_ONCE(info->control.rates[0].flags & IEEE80211_TX_RC_MCS &&
 			  !ieee80211_is_data(fc),
 			  "Got a HT rate (flags:0x%x/mcs:%d/fc:0x%x/state:%d) for a non data frame\n",
 			  info->control.rates[0].flags,
 			  info->control.rates[0].idx,
-			  le16_to_cpu(fc), sta ? mvmsta->sta_state : -1);
+			  le16_to_cpu(fc),
+			  sta ? iwl_mvm_sta_from_mac80211(sta)->sta_state : -1);
 
 		rate_idx = info->control.rates[0].idx;
 	}
-- 
2.31.1