(bug report) iwlwifi: inconsitent NULL checking

Commit Message

Dan Carpenter Nov. 26, 2015, 7:44 p.m. UTC

There are two issues in Smatch that would need to be fixed:



If apply that patch (with changes for your system) and run
kchecker drivers/net/wireless/intel/iwlwifi/mvm/rs.c then it prints:

drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2800 rs_get_rate() implied: lq_sta = '0,4096-2117777777777777777'
drivers/net/wireless/intel/iwlwifi/mvm/rs.c:2805 rs_get_rate() implied: mvm_sta = 's64min-(-1),1-s64max'

The first problem is that it doesn't see that if mvm_sta is non-NULL
then that implies lq_sta is non-NULL.  But even if that worked, after we
do the function call, it sees that the function that mvm_sta is non-NULL
but it wouldn't see that that means lq_sta is non-NULL.  It's not so
terribly far from working but it's not there yet.

regards,
dan carpenter
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Comments

Johannes Berg Nov. 26, 2015, 8:21 p.m. UTC | #1

On Thu, 2015-11-26 at 22:44 +0300, Dan Carpenter wrote:
> 
> The first problem is that it doesn't see that if mvm_sta is non-NULL
> then that implies lq_sta is non-NULL.  But even if that worked, after
> we do the function call, it sees that the function that mvm_sta is
> non-NULL but it wouldn't see that that means lq_sta is non-
> NULL.  It's not so terribly far from working but it's not there yet.
> 

Ah, yes, I completely forgot that it's two (related) variables :)

johannes
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Patch

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
index d1ad103..d3bc193 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
@@ -2767,6 +2767,7 @@  static void rs_initialize_lq(struct iwl_mvm *mvm,
 	iwl_mvm_send_lq_cmd(mvm, &lq_sta->lq, init);
 }
 
+#include "/home/dcarpenter/progs/smatch/devel/check_debug.h"
 static void rs_get_rate(void *mvm_r, struct ieee80211_sta *sta, void *mvm_sta,
 			struct ieee80211_tx_rate_control *txrc)
 {
@@ -2795,9 +2796,13 @@  static void rs_get_rate(void *mvm_r, struct ieee80211_sta *sta, void *mvm_sta,
 		mvm_sta = NULL;
 	}
 
+	if (mvm_sta)
+		__smatch_implied(lq_sta);
+
 	/* Send management frames and NO_ACK data using lowest rate. */
 	if (rate_control_send_low(sta, mvm_sta, txrc))
 		return;
+	__smatch_implied(mvm_sta);
 
 	iwl_mvm_hwrate_to_tx_rate(lq_sta->last_rate_n_flags,
 				  info->band, &info->control.rates[0]);