From 8036e90f92aae2784b855a0007ae2d8154d28b3c Mon Sep 17 00:00:00 2001 From: Parvi Kaustubhi Date: Tue, 11 Dec 2018 14:15:42 -0800 Subject: [PATCH] IB/usnic: Fix potential deadlock Acquiring the rtnl lock while holding usdev_lock could result in a deadlock. For example: usnic_ib_query_port() | mutex_lock(&us_ibdev->usdev_lock) | ib_get_eth_speed() | rtnl_lock() rtnl_lock() | usnic_ib_netdevice_event() | mutex_lock(&us_ibdev->usdev_lock) This commit moves the usdev_lock acquisition after the rtnl lock has been released. This is safe to do because usdev_lock is not protecting anything being accessed in ib_get_eth_speed(). Hence, the correct order of holding locks (rtnl -> usdev_lock) is not violated. Signed-off-by: Parvi Kaustubhi Signed-off-by: Jason Gunthorpe --- drivers/infiniband/hw/usnic/usnic_ib_verbs.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/hw/usnic/usnic_ib_verbs.c b/drivers/infiniband/hw/usnic/usnic_ib_verbs.c index 1b9f69d65111..1d4abef17e38 100644 --- a/drivers/infiniband/hw/usnic/usnic_ib_verbs.c +++ b/drivers/infiniband/hw/usnic/usnic_ib_verbs.c @@ -336,13 +336,16 @@ int usnic_ib_query_port(struct ib_device *ibdev, u8 port, usnic_dbg("\n"); - mutex_lock(&us_ibdev->usdev_lock); if (ib_get_eth_speed(ibdev, port, &props->active_speed, - &props->active_width)) { - mutex_unlock(&us_ibdev->usdev_lock); + &props->active_width)) return -EINVAL; - } + /* + * usdev_lock is acquired after (and not before) ib_get_eth_speed call + * because acquiring rtnl_lock in ib_get_eth_speed, while holding + * usdev_lock could lead to a deadlock. + */ + mutex_lock(&us_ibdev->usdev_lock); /* props being zeroed by the caller, avoid zeroing it here */ props->lid = 0; -- 2.45.2