4.4-stable review patch. If anyone has any objections, please let me know.
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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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c @@ -473,6 +473,9 @@ static int ipoib_mcast_join(struct net_d !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; @@ -631,8 +634,6 @@ void ipoib_mcast_join_task(struct work_s 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; @@ -652,11 +653,9 @@ out: 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); }