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Subject[PATCH AUTOSEL 4.14 08/46] IB/ipoib: Fix lockdep issue found on ipoib_ib_dev_heavy_flush
Date
From: Alex Vesker <valex@mellanox.com>

[ Upstream commit 1f80bd6a6cc8358b81194e1f5fc16449947396ec ]

The locking order of vlan_rwsem (LOCK A) and then rtnl (LOCK B),
contradicts other flows such as ipoib_open possibly causing a deadlock.
To prevent this deadlock heavy flush is called with RTNL locked and
only then tries to acquire vlan_rwsem.
This deadlock is possible only when there are child interfaces.

[ 140.941758] ======================================================
[ 140.946276] WARNING: possible circular locking dependency detected
[ 140.950950] 4.15.0-rc1+ #9 Tainted: G O
[ 140.954797] ------------------------------------------------------
[ 140.959424] kworker/u32:1/146 is trying to acquire lock:
[ 140.963450] (rtnl_mutex){+.+.}, at: [<ffffffffc083516a>] __ipoib_ib_dev_flush+0x2da/0x4e0 [ib_ipoib]
[ 140.970006]
but task is already holding lock:
[ 140.975141] (&priv->vlan_rwsem){++++}, at: [<ffffffffc0834ee1>] __ipoib_ib_dev_flush+0x51/0x4e0 [ib_ipoib]
[ 140.982105]
which lock already depends on the new lock.
[ 140.990023]
the existing dependency chain (in reverse order) is:
[ 140.998650]
-> #1 (&priv->vlan_rwsem){++++}:
[ 141.005276] down_read+0x4d/0xb0
[ 141.009560] ipoib_open+0xad/0x120 [ib_ipoib]
[ 141.014400] __dev_open+0xcb/0x140
[ 141.017919] __dev_change_flags+0x1a4/0x1e0
[ 141.022133] dev_change_flags+0x23/0x60
[ 141.025695] devinet_ioctl+0x704/0x7d0
[ 141.029156] sock_do_ioctl+0x20/0x50
[ 141.032526] sock_ioctl+0x221/0x300
[ 141.036079] do_vfs_ioctl+0xa6/0x6d0
[ 141.039656] SyS_ioctl+0x74/0x80
[ 141.042811] entry_SYSCALL_64_fastpath+0x1f/0x96
[ 141.046891]
-> #0 (rtnl_mutex){+.+.}:
[ 141.051701] lock_acquire+0xd4/0x220
[ 141.055212] __mutex_lock+0x88/0x970
[ 141.058631] __ipoib_ib_dev_flush+0x2da/0x4e0 [ib_ipoib]
[ 141.063160] __ipoib_ib_dev_flush+0x71/0x4e0 [ib_ipoib]
[ 141.067648] process_one_work+0x1f5/0x610
[ 141.071429] worker_thread+0x4a/0x3f0
[ 141.074890] kthread+0x141/0x180
[ 141.078085] ret_from_fork+0x24/0x30
[ 141.081559]

other info that might help us debug this:
[ 141.088967] Possible unsafe locking scenario:
[ 141.094280] CPU0 CPU1
[ 141.097953] ---- ----
[ 141.101640] lock(&priv->vlan_rwsem);
[ 141.104771] lock(rtnl_mutex);
[ 141.109207] lock(&priv->vlan_rwsem);
[ 141.114032] lock(rtnl_mutex);
[ 141.116800]
*** DEADLOCK ***

Fixes: b4b678b06f6e ("IB/ipoib: Grab rtnl lock on heavy flush when calling ndo_open/stop")
Signed-off-by: Alex Vesker <valex@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/ulp/ipoib/ipoib_ib.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
index c97384c914a4..d77e8e2ae05f 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
@@ -1203,13 +1203,10 @@ static void __ipoib_ib_dev_flush(struct ipoib_dev_priv *priv,
ipoib_ib_dev_down(dev);

if (level == IPOIB_FLUSH_HEAVY) {
- rtnl_lock();
if (test_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
ipoib_ib_dev_stop(dev);

- result = ipoib_ib_dev_open(dev);
- rtnl_unlock();
- if (result)
+ if (ipoib_ib_dev_open(dev))
return;

if (netif_queue_stopped(dev))
@@ -1249,7 +1246,9 @@ void ipoib_ib_dev_flush_heavy(struct work_struct *work)
struct ipoib_dev_priv *priv =
container_of(work, struct ipoib_dev_priv, flush_heavy);

+ rtnl_lock();
__ipoib_ib_dev_flush(priv, IPOIB_FLUSH_HEAVY, 0);
+ rtnl_unlock();
}

void ipoib_ib_dev_cleanup(struct net_device *dev)
--
2.17.1
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