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Subject[ 095/184] IPoIB: Fix use-after-free of multicast object
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

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

From: Patrick McHardy <kaber@trash.net>

commit bea1e22df494a729978e7f2c54f7bda328f74bc3 upstream.

Fix a crash in ipoib_mcast_join_task(). (with help from Or Gerlitz)

Commit c8c2afe360b7 ("IPoIB: Use rtnl lock/unlock when changing device
flags") added a call to rtnl_lock() in ipoib_mcast_join_task(), which
is run from the ipoib_workqueue, and hence the workqueue can't be
flushed from the context of ipoib_stop().

In the current code, ipoib_stop() (which doesn't flush the workqueue)
calls ipoib_mcast_dev_flush(), which goes and deletes all the
multicast entries. This takes place without any synchronization with
a possible running instance of ipoib_mcast_join_task() for the same
ipoib device, leading to a crash due to NULL pointer dereference.

Fix this by making sure that the workqueue is flushed before
ipoib_mcast_dev_flush() is called. To make that possible, we move the
RTNL-lock wrapped code to ipoib_mcast_join_finish().

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
drivers/infiniband/ulp/ipoib/ipoib_main.c | 2 +-
drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 19 ++++++++++---------
2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index b4b2257..f6a23ec 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -157,7 +157,7 @@ static int ipoib_stop(struct net_device *dev)

netif_stop_queue(dev);

- ipoib_ib_dev_down(dev, 0);
+ ipoib_ib_dev_down(dev, 1);
ipoib_ib_dev_stop(dev, 0);

if (!test_bit(IPOIB_FLAG_SUBINTERFACE, &priv->flags)) {
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index 8763c1e..bd656a7 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -188,7 +188,9 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,

mcast->mcmember = *mcmember;

- /* Set the cached Q_Key before we attach if it's the broadcast group */
+ /* Set the multicast MTU and cached Q_Key before we attach if it's
+ * the broadcast group.
+ */
if (!memcmp(mcast->mcmember.mgid.raw, priv->dev->broadcast + 4,
sizeof (union ib_gid))) {
spin_lock_irq(&priv->lock);
@@ -196,10 +198,17 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
spin_unlock_irq(&priv->lock);
return -EAGAIN;
}
+ priv->mcast_mtu = IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
priv->qkey = be32_to_cpu(priv->broadcast->mcmember.qkey);
spin_unlock_irq(&priv->lock);
priv->tx_wr.wr.ud.remote_qkey = priv->qkey;
set_qkey = 1;
+
+ if (!ipoib_cm_admin_enabled(dev)) {
+ rtnl_lock();
+ dev_set_mtu(dev, min(priv->mcast_mtu, priv->admin_mtu));
+ rtnl_unlock();
+ }
}

if (!test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags)) {
@@ -588,14 +597,6 @@ void ipoib_mcast_join_task(struct work_struct *work)
return;
}

- priv->mcast_mtu = IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
-
- if (!ipoib_cm_admin_enabled(dev)) {
- rtnl_lock();
- dev_set_mtu(dev, min(priv->mcast_mtu, priv->admin_mtu));
- rtnl_unlock();
- }
-
ipoib_dbg_mcast(priv, "successfully joined all multicast groups\n");

clear_bit(IPOIB_MCAST_RUN, &priv->flags);
--
1.7.12.2.21.g234cd45.dirty




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