commit a042994dd377d86bff9446ee76151ceb6267c9ba
author Luis R. Rodriguez <mcgrof@qca.qualcomm.com> Mon Nov 28 16:47:15 2011 -0500
committer John W. Linville <linville@tuxdriver.com> Wed Nov 30 14:16:31 2011 -0500
tree 2e7a30ca3f6ce9ecb06179abce92bc9520981506
parent 2a1e0fd175dcfd72096ba9291d31e3b1b5342e60

cfg80211: fix race on init and driver registration

There is a theoretical race that if hit will trigger
a crash. The race is between when we issue the first
regulatory hint, regulatory_hint_core(), gets processed
by the workqueue and between when the first device
gets registered to the wireless core. This is not easy
to reproduce but it was easy to do so through the
regulatory simulator I have been working on. This
is a port of the fix I implemented there [1].

[1] https://github.com/mcgrof/regsim/commit/a246ccf81f059cb662eee288aa13100f631e4cc8

Cc: stable@vger.kernel.org
Cc: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/reg.c

diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index 186b7f2..0ec4071 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -55,8 +55,17 @@
 #define REG_DBG_PRINT(args...)
 #endif
 
+static struct regulatory_request core_request_world = {
+	.initiator = NL80211_REGDOM_SET_BY_CORE,
+	.alpha2[0] = '0',
+	.alpha2[1] = '0',
+	.intersect = false,
+	.processed = true,
+	.country_ie_env = ENVIRON_ANY,
+};
+
 /* Receipt of information from last regulatory request */
-static struct regulatory_request *last_request;
+static struct regulatory_request *last_request = &core_request_world;
 
 /* To trigger userspace events */
 static struct platform_device *reg_pdev;
@@ -148,7 +157,7 @@
 module_param(ieee80211_regdom, charp, 0444);
 MODULE_PARM_DESC(ieee80211_regdom, "IEEE 802.11 regulatory domain code");
 
-static void reset_regdomains(void)
+static void reset_regdomains(bool full_reset)
 {
 	/* avoid freeing static information or freeing something twice */
 	if (cfg80211_regdomain == cfg80211_world_regdom)
@@ -163,6 +172,13 @@
 
 	cfg80211_world_regdom = &world_regdom;
 	cfg80211_regdomain = NULL;
+
+	if (!full_reset)
+		return;
+
+	if (last_request != &core_request_world)
+		kfree(last_request);
+	last_request = &core_request_world;
 }
 
 /*
@@ -173,7 +189,7 @@
 {
 	BUG_ON(!last_request);
 
-	reset_regdomains();
+	reset_regdomains(false);
 
 	cfg80211_world_regdom = rd;
 	cfg80211_regdomain = rd;
@@ -1405,7 +1421,8 @@
 	}
 
 new_request:
-	kfree(last_request);
+	if (last_request != &core_request_world)
+		kfree(last_request);
 
 	last_request = pending_request;
 	last_request->intersect = intersect;
@@ -1575,9 +1592,6 @@
 {
 	struct regulatory_request *request;
 
-	kfree(last_request);
-	last_request = NULL;
-
 	request = kzalloc(sizeof(struct regulatory_request),
 			  GFP_KERNEL);
 	if (!request)
@@ -1775,7 +1789,7 @@
 	mutex_lock(&cfg80211_mutex);
 	mutex_lock(&reg_mutex);
 
-	reset_regdomains();
+	reset_regdomains(true);
 	restore_alpha2(alpha2, reset_user);
 
 	/*
@@ -2044,7 +2058,7 @@
 		int r;
 
 		if (last_request->initiator != NL80211_REGDOM_SET_BY_DRIVER) {
-			reset_regdomains();
+			reset_regdomains(false);
 			cfg80211_regdomain = rd;
 			return 0;
 		}
@@ -2065,7 +2079,7 @@
 		if (r)
 			return r;
 
-		reset_regdomains();
+		reset_regdomains(false);
 		cfg80211_regdomain = rd;
 		return 0;
 	}
@@ -2090,7 +2104,7 @@
 
 		rd = NULL;
 
-		reset_regdomains();
+		reset_regdomains(false);
 		cfg80211_regdomain = intersected_rd;
 
 		return 0;
@@ -2110,7 +2124,7 @@
 	kfree(rd);
 	rd = NULL;
 
-	reset_regdomains();
+	reset_regdomains(false);
 	cfg80211_regdomain = intersected_rd;
 
 	return 0;
@@ -2263,11 +2277,8 @@
 	mutex_lock(&cfg80211_mutex);
 	mutex_lock(&reg_mutex);
 
-	reset_regdomains();
+	reset_regdomains(true);
 
-	kfree(last_request);
-
-	last_request = NULL;
 	dev_set_uevent_suppress(&reg_pdev->dev, true);
 
 	platform_device_unregister(reg_pdev);