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Subject[PATCH AUTOSEL for 4.9 061/190] IB/ipoib: Fix deadlock between ipoib_stop and mcast join flow
Date
From: Feras Daoud <ferasda@mellanox.com>

[ Upstream commit 3e31a490e01a6e67cbe9f6e1df2f3ff0fbf48972 ]

Before calling ipoib_stop, rtnl_lock should be taken, then
the flow clears the IPOIB_FLAG_ADMIN_UP and IPOIB_FLAG_OPER_UP
flags, and waits for mcast completion if IPOIB_MCAST_FLAG_BUSY
is set.

On the other hand, the flow of multicast join task initializes
a mcast completion, sets the IPOIB_MCAST_FLAG_BUSY and calls
ipoib_mcast_join. If IPOIB_FLAG_OPER_UP flag is not set, this
call returns EINVAL without setting the mcast completion and
leads to a deadlock.

ipoib_stop |
| |
clear_bit(IPOIB_FLAG_ADMIN_UP) |
| |
Context Switch |
| ipoib_mcast_join_task
| |
| spin_lock_irq(lock)
| |
| init_completion(mcast)
| |
| set_bit(IPOIB_MCAST_FLAG_BUSY)
| |
| Context Switch
| |
clear_bit(IPOIB_FLAG_OPER_UP) |
| |
spin_lock_irqsave(lock) |
| |
Context Switch |
| ipoib_mcast_join
| return (-EINVAL)
| |
| spin_unlock_irq(lock)
| |
| Context Switch
| |
ipoib_mcast_dev_flush |
wait_for_completion(mcast) |

ipoib_stop will wait for mcast completion for ever, and will
not release the rtnl_lock. As a result panic occurs with the
following trace:

[13441.639268] Call Trace:
[13441.640150] [<ffffffff8168b579>] schedule+0x29/0x70
[13441.641038] [<ffffffff81688fc9>] schedule_timeout+0x239/0x2d0
[13441.641914] [<ffffffff810bc017>] ? complete+0x47/0x50
[13441.642765] [<ffffffff810a690d>] ? flush_workqueue_prep_pwqs+0x16d/0x200
[13441.643580] [<ffffffff8168b956>] wait_for_completion+0x116/0x170
[13441.644434] [<ffffffff810c4ec0>] ? wake_up_state+0x20/0x20
[13441.645293] [<ffffffffa05af170>] ipoib_mcast_dev_flush+0x150/0x190 [ib_ipoib]
[13441.646159] [<ffffffffa05ac967>] ipoib_ib_dev_down+0x37/0x60 [ib_ipoib]
[13441.647013] [<ffffffffa05a4805>] ipoib_stop+0x75/0x150 [ib_ipoib]

Fixes: 08bc327629cb ("IB/ipoib: fix for rare multicast join race condition")
Signed-off-by: Feras Daoud <ferasda@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index fddff403d5d2..8f36fda48b87 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -487,6 +487,9 @@ static int ipoib_mcast_join(struct net_device *dev, struct ipoib_mcast *mcast)
!test_bit(IPOIB_FLAG_OPER_UP, &priv->flags))
return -EINVAL;

+ init_completion(&mcast->done);
+ set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
+
ipoib_dbg_mcast(priv, "joining MGID %pI6\n", mcast->mcmember.mgid.raw);

rec.mgid = mcast->mcmember.mgid;
@@ -645,8 +648,6 @@ void ipoib_mcast_join_task(struct work_struct *work)
if (mcast->backoff == 1 ||
time_after_eq(jiffies, mcast->delay_until)) {
/* Found the next unjoined group */
- init_completion(&mcast->done);
- set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
if (ipoib_mcast_join(dev, mcast)) {
spin_unlock_irq(&priv->lock);
return;
@@ -666,11 +667,9 @@ void ipoib_mcast_join_task(struct work_struct *work)
queue_delayed_work(priv->wq, &priv->mcast_task,
delay_until - jiffies);
}
- if (mcast) {
- init_completion(&mcast->done);
- set_bit(IPOIB_MCAST_FLAG_BUSY, &mcast->flags);
+ if (mcast)
ipoib_mcast_join(dev, mcast);
- }
+
spin_unlock_irq(&priv->lock);
}

--
2.14.1
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