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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Andrea Righi <andrea.righi@canonical.com>,
	"David S . Miller" <davem@davemloft.net>,
	Sasha Levin <sashal@kernel.org>,
	xen-devel@lists.xenproject.org, netdev@vger.kernel.org
Subject: [PATCH AUTOSEL 5.4 15/17] xen-netfront: fix potential deadlock in xennet_remove()
Date: Mon, 27 Jul 2020 19:24:18 -0400	[thread overview]
Message-ID: <20200727232420.717684-15-sashal@kernel.org> (raw)
In-Reply-To: <20200727232420.717684-1-sashal@kernel.org>

From: Andrea Righi <andrea.righi@canonical.com>

[ Upstream commit c2c633106453611be07821f53dff9e93a9d1c3f0 ]

There's a potential race in xennet_remove(); this is what the driver is
doing upon unregistering a network device:

  1. state = read bus state
  2. if state is not "Closed":
  3.    request to set state to "Closing"
  4.    wait for state to be set to "Closing"
  5.    request to set state to "Closed"
  6.    wait for state to be set to "Closed"

If the state changes to "Closed" immediately after step 1 we are stuck
forever in step 4, because the state will never go back from "Closed" to
"Closing".

Make sure to check also for state == "Closed" in step 4 to prevent the
deadlock.

Also add a 5 sec timeout any time we wait for the bus state to change,
to avoid getting stuck forever in wait_event().

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/xen-netfront.c | 64 +++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 22 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 482c6c8b0fb7e..88280057e0321 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -63,6 +63,8 @@ module_param_named(max_queues, xennet_max_queues, uint, 0644);
 MODULE_PARM_DESC(max_queues,
 		 "Maximum number of queues per virtual interface");
 
+#define XENNET_TIMEOUT  (5 * HZ)
+
 static const struct ethtool_ops xennet_ethtool_ops;
 
 struct netfront_cb {
@@ -1334,12 +1336,15 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 
 	netif_carrier_off(netdev);
 
-	xenbus_switch_state(dev, XenbusStateInitialising);
-	wait_event(module_wq,
-		   xenbus_read_driver_state(dev->otherend) !=
-		   XenbusStateClosed &&
-		   xenbus_read_driver_state(dev->otherend) !=
-		   XenbusStateUnknown);
+	do {
+		xenbus_switch_state(dev, XenbusStateInitialising);
+		err = wait_event_timeout(module_wq,
+				 xenbus_read_driver_state(dev->otherend) !=
+				 XenbusStateClosed &&
+				 xenbus_read_driver_state(dev->otherend) !=
+				 XenbusStateUnknown, XENNET_TIMEOUT);
+	} while (!err);
+
 	return netdev;
 
  exit:
@@ -2139,28 +2144,43 @@ static const struct attribute_group xennet_dev_group = {
 };
 #endif /* CONFIG_SYSFS */
 
-static int xennet_remove(struct xenbus_device *dev)
+static void xennet_bus_close(struct xenbus_device *dev)
 {
-	struct netfront_info *info = dev_get_drvdata(&dev->dev);
-
-	dev_dbg(&dev->dev, "%s\n", dev->nodename);
+	int ret;
 
-	if (xenbus_read_driver_state(dev->otherend) != XenbusStateClosed) {
+	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+		return;
+	do {
 		xenbus_switch_state(dev, XenbusStateClosing);
-		wait_event(module_wq,
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateClosing ||
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateUnknown);
+		ret = wait_event_timeout(module_wq,
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosing ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosed ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateUnknown,
+				   XENNET_TIMEOUT);
+	} while (!ret);
+
+	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+		return;
 
+	do {
 		xenbus_switch_state(dev, XenbusStateClosed);
-		wait_event(module_wq,
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateClosed ||
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateUnknown);
-	}
+		ret = wait_event_timeout(module_wq,
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosed ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateUnknown,
+				   XENNET_TIMEOUT);
+	} while (!ret);
+}
+
+static int xennet_remove(struct xenbus_device *dev)
+{
+	struct netfront_info *info = dev_get_drvdata(&dev->dev);
 
+	xennet_bus_close(dev);
 	xennet_disconnect_backend(info);
 
 	if (info->netdev->reg_state == NETREG_REGISTERED)
-- 
2.25.1


WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sasha Levin <sashal@kernel.org>,
	Andrea Righi <andrea.righi@canonical.com>,
	netdev@vger.kernel.org, "David S . Miller" <davem@davemloft.net>,
	xen-devel@lists.xenproject.org
Subject: [PATCH AUTOSEL 5.4 15/17] xen-netfront: fix potential deadlock in xennet_remove()
Date: Mon, 27 Jul 2020 19:24:18 -0400	[thread overview]
Message-ID: <20200727232420.717684-15-sashal@kernel.org> (raw)
In-Reply-To: <20200727232420.717684-1-sashal@kernel.org>

From: Andrea Righi <andrea.righi@canonical.com>

[ Upstream commit c2c633106453611be07821f53dff9e93a9d1c3f0 ]

There's a potential race in xennet_remove(); this is what the driver is
doing upon unregistering a network device:

  1. state = read bus state
  2. if state is not "Closed":
  3.    request to set state to "Closing"
  4.    wait for state to be set to "Closing"
  5.    request to set state to "Closed"
  6.    wait for state to be set to "Closed"

If the state changes to "Closed" immediately after step 1 we are stuck
forever in step 4, because the state will never go back from "Closed" to
"Closing".

Make sure to check also for state == "Closed" in step 4 to prevent the
deadlock.

Also add a 5 sec timeout any time we wait for the bus state to change,
to avoid getting stuck forever in wait_event().

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/xen-netfront.c | 64 +++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 22 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 482c6c8b0fb7e..88280057e0321 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -63,6 +63,8 @@ module_param_named(max_queues, xennet_max_queues, uint, 0644);
 MODULE_PARM_DESC(max_queues,
 		 "Maximum number of queues per virtual interface");
 
+#define XENNET_TIMEOUT  (5 * HZ)
+
 static const struct ethtool_ops xennet_ethtool_ops;
 
 struct netfront_cb {
@@ -1334,12 +1336,15 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 
 	netif_carrier_off(netdev);
 
-	xenbus_switch_state(dev, XenbusStateInitialising);
-	wait_event(module_wq,
-		   xenbus_read_driver_state(dev->otherend) !=
-		   XenbusStateClosed &&
-		   xenbus_read_driver_state(dev->otherend) !=
-		   XenbusStateUnknown);
+	do {
+		xenbus_switch_state(dev, XenbusStateInitialising);
+		err = wait_event_timeout(module_wq,
+				 xenbus_read_driver_state(dev->otherend) !=
+				 XenbusStateClosed &&
+				 xenbus_read_driver_state(dev->otherend) !=
+				 XenbusStateUnknown, XENNET_TIMEOUT);
+	} while (!err);
+
 	return netdev;
 
  exit:
@@ -2139,28 +2144,43 @@ static const struct attribute_group xennet_dev_group = {
 };
 #endif /* CONFIG_SYSFS */
 
-static int xennet_remove(struct xenbus_device *dev)
+static void xennet_bus_close(struct xenbus_device *dev)
 {
-	struct netfront_info *info = dev_get_drvdata(&dev->dev);
-
-	dev_dbg(&dev->dev, "%s\n", dev->nodename);
+	int ret;
 
-	if (xenbus_read_driver_state(dev->otherend) != XenbusStateClosed) {
+	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+		return;
+	do {
 		xenbus_switch_state(dev, XenbusStateClosing);
-		wait_event(module_wq,
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateClosing ||
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateUnknown);
+		ret = wait_event_timeout(module_wq,
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosing ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosed ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateUnknown,
+				   XENNET_TIMEOUT);
+	} while (!ret);
+
+	if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+		return;
 
+	do {
 		xenbus_switch_state(dev, XenbusStateClosed);
-		wait_event(module_wq,
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateClosed ||
-			   xenbus_read_driver_state(dev->otherend) ==
-			   XenbusStateUnknown);
-	}
+		ret = wait_event_timeout(module_wq,
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateClosed ||
+				   xenbus_read_driver_state(dev->otherend) ==
+				   XenbusStateUnknown,
+				   XENNET_TIMEOUT);
+	} while (!ret);
+}
+
+static int xennet_remove(struct xenbus_device *dev)
+{
+	struct netfront_info *info = dev_get_drvdata(&dev->dev);
 
+	xennet_bus_close(dev);
 	xennet_disconnect_backend(info);
 
 	if (info->netdev->reg_state == NETREG_REGISTERED)
-- 
2.25.1



  parent reply	other threads:[~2020-07-27 23:27 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27 23:24 [PATCH AUTOSEL 5.4 01/17] usb: hso: Fix debug compile warning on sparc32 Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 02/17] selftests: fib_nexthop_multiprefix: fix cleanup() netns deletion Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 03/17] qed: Disable "MFW indication via attention" SPAM every 5 minutes Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 04/17] selftests: net: ip_defrag: modprobe missing nf_defrag_ipv6 support Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 05/17] habanalabs: prevent possible out-of-bounds array access Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 06/17] nfc: s3fwrn5: add missing release on skb in s3fwrn5_recv_frame Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 07/17] scsi: core: Run queue in case of I/O resource contention failure Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 08/17] parisc: add support for cmpxchg on u8 pointers Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 09/17] net: ethernet: ravb: exit if re-initialization fails in tx timeout Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 10/17] drivers/net/wan/x25_asy: Fix to make it work Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 11/17] Revert "i2c: cadence: Fix the hold bit setting" Sasha Levin
2020-07-27 23:24   ` Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 12/17] x86/unwind/orc: Fix ORC for newly forked tasks Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 13/17] x86/stacktrace: Fix reliable check for empty user task stacks Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 14/17] cxgb4: add missing release on skb in uld_send() Sasha Levin
2020-07-27 23:24 ` Sasha Levin [this message]
2020-07-27 23:24   ` [PATCH AUTOSEL 5.4 15/17] xen-netfront: fix potential deadlock in xennet_remove() Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 16/17] RISC-V: Set maximum number of mapped pages correctly Sasha Levin
2020-07-27 23:24   ` Sasha Levin
2020-07-27 23:24 ` [PATCH AUTOSEL 5.4 17/17] drivers/net/wan: lapb: Corrected the usage of skb_cow Sasha Levin

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