RE: [bug report] iwlwifi: mvm: toggle tx antenna if tx fails during connection establishment

["Stern, Avraham" <avraham.stern@intel.com>]

Hi Dan,

The offending patch that caused the Smatch complaint is:
"iwlwifi: mvm: add explicit check for non-data frames in get Tx rate"

this patch adds an unconditional dereference of the  sta  parameter in iwl_mvm_get_tx_rate().
Before that, all the code paths check for the NULL option.

(this patch is from the recent days, that's why Smatch only complains now).

Regards,
Avi


-----Original Message-----
From: Dan Carpenter <dan.carpenter@oracle.com> 
Sent: Wednesday, February 10, 2021 12:55
To: Stern, Avraham <avraham.stern@intel.com>
Cc: linux-wireless@vger.kernel.org
Subject: [bug report] iwlwifi: mvm: toggle tx antenna if tx fails during connection establishment

[ Sorry, I don't know why Smatch is warning about a three year old bug
  and I'm not sure that it's blaming the correct commit but the warning
  looks correct.  - dan ]

Hello Avraham Stern,

This is a semi-automatic email about new static checker warnings.

The patch 0dde2440a77f: "iwlwifi: mvm: toggle tx antenna if tx fails during connection establishment" from Jul 11, 2018, leads to the following Smatch complaint:

    drivers/net/wireless/intel/iwlwifi/mvm/tx.c:356 iwl_mvm_set_tx_cmd_rate()
    error: we previously assumed 'sta' could be null (see line 341)

drivers/net/wireless/intel/iwlwifi/mvm/tx.c
   340	
   341		if (ieee80211_is_data(fc) && sta) {
                                             ^^^ This assumes that "sta" can be NULL.

   342			struct iwl_mvm_sta *mvmsta = iwl_mvm_sta_from_mac80211(sta);
   343	
   344			if (mvmsta->sta_state >= IEEE80211_STA_AUTHORIZED) {
   345				tx_cmd->initial_rate_index = 0;
   346				tx_cmd->tx_flags |= cpu_to_le32(TX_CMD_FLG_STA_RATE);
   347				return;
   348			}
   349		} else if (ieee80211_is_back_req(fc)) {
   350			tx_cmd->tx_flags |=
   351				cpu_to_le32(TX_CMD_FLG_ACK | TX_CMD_FLG_BAR);
   352		}
   353	
   354		/* Set the rate in the TX cmd */
   355		tx_cmd->rate_n_flags =
   356			cpu_to_le32(iwl_mvm_get_tx_rate_n_flags(mvm, info, sta, fc));
                                                                           ^^^ It is dereferenced unconsiditionally inside the function.

   357	}
   358	

See also:
drivers/net/wireless/intel/iwlwifi/mvm/tx.c:486 iwl_mvm_set_tx_params() error: we previously assumed 'sta' could be null (see line 482)

regards,
dan carpenter
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