linux-kernel - [088/104] cfg80211: fix race on init and driver registration

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Message-Id: <20111207161222.029403284@clark.kroah.org>
Date:	Wed, 07 Dec 2011 08:12:30 -0800
From:	Greg KH <gregkh@...e.de>
To:	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Cc:	<torvalds@...ux-foundation.org>, <akpm@...ux-foundation.org>,
	<alan@...rguk.ukuu.org.uk>,
	Johannes Berg <johannes.berg@...el.com>,
	"Luis R. Rodriguez" <mcgrof@....qualcomm.com>,
	"John W. Linville" <linville@...driver.com>
Subject: [088/104] cfg80211: fix race on init and driver registration

3.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Luis R. Rodriguez" <mcgrof@....qualcomm.com>

commit a042994dd377d86bff9446ee76151ceb6267c9ba upstream.

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: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@....qualcomm.com>
Signed-off-by: John W. Linville <linville@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 net/wireless/reg.c |   43 +++++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 16 deletions(-)

--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -57,8 +57,17 @@
 #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;
@@ -150,7 +159,7 @@ static char user_alpha2[2];
 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)
@@ -165,6 +174,13 @@ static void reset_regdomains(void)
 
 	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;
 }
 
 /*
@@ -175,7 +191,7 @@ static void update_world_regdomain(const
 {
 	BUG_ON(!last_request);
 
-	reset_regdomains();
+	reset_regdomains(false);
 
 	cfg80211_world_regdom = rd;
 	cfg80211_regdomain = rd;
@@ -1396,7 +1412,8 @@ static int __regulatory_hint(struct wiph
 	}
 
 new_request:
-	kfree(last_request);
+	if (last_request != &core_request_world)
+		kfree(last_request);
 
 	last_request = pending_request;
 	last_request->intersect = intersect;
@@ -1566,9 +1583,6 @@ static int regulatory_hint_core(const ch
 {
 	struct regulatory_request *request;
 
-	kfree(last_request);
-	last_request = NULL;
-
 	request = kzalloc(sizeof(struct regulatory_request),
 			  GFP_KERNEL);
 	if (!request)
@@ -1766,7 +1780,7 @@ static void restore_regulatory_settings(
 	mutex_lock(&cfg80211_mutex);
 	mutex_lock(&reg_mutex);
 
-	reset_regdomains();
+	reset_regdomains(true);
 	restore_alpha2(alpha2, reset_user);
 
 	/*
@@ -2035,7 +2049,7 @@ static int __set_regdom(const struct iee
 		int r;
 
 		if (last_request->initiator != NL80211_REGDOM_SET_BY_DRIVER) {
-			reset_regdomains();
+			reset_regdomains(false);
 			cfg80211_regdomain = rd;
 			return 0;
 		}
@@ -2056,7 +2070,7 @@ static int __set_regdom(const struct iee
 		if (r)
 			return r;
 
-		reset_regdomains();
+		reset_regdomains(false);
 		cfg80211_regdomain = rd;
 		return 0;
 	}
@@ -2081,7 +2095,7 @@ static int __set_regdom(const struct iee
 
 		rd = NULL;
 
-		reset_regdomains();
+		reset_regdomains(false);
 		cfg80211_regdomain = intersected_rd;
 
 		return 0;
@@ -2101,7 +2115,7 @@ static int __set_regdom(const struct iee
 	kfree(rd);
 	rd = NULL;
 
-	reset_regdomains();
+	reset_regdomains(false);
 	cfg80211_regdomain = intersected_rd;
 
 	return 0;
@@ -2254,11 +2268,8 @@ void /* __init_or_exit */ regulatory_exi
 	mutex_lock(&cfg80211_mutex);
 	mutex_lock(&reg_mutex);
 
-	reset_regdomains();
-
-	kfree(last_request);
+	reset_regdomains(true);
 
-	last_request = NULL;
 	dev_set_uevent_suppress(&reg_pdev->dev, true);
 
 	platform_device_unregister(reg_pdev);


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