From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:45032 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932273AbcL0Nmu (ORCPT ); Tue, 27 Dec 2016 08:42:50 -0500 From: Leon Romanovsky To: dledford@redhat.com Cc: linux-rdma@vger.kernel.org, Feras Daoud , , Or Gerlitz , Erez Shitrit Subject: [PATCH rdma-next 4/9] IB/ipoib: Fix deadlock between rmmod and set_mode Date: Tue, 27 Dec 2016 15:39:06 +0200 Message-Id: <20161227133911.14340-5-leon@kernel.org> In-Reply-To: <20161227133911.14340-1-leon@kernel.org> References: <20161227133911.14340-1-leon@kernel.org> Sender: stable-owner@vger.kernel.org List-ID: From: Feras Daoud When calling set_mode from sys/fs, the call flow locks the sys/fs lock first and then tries to lock rtnl_lock (when calling ipoib_set_mod). On the other hand, the rmmod call flow takes the rtnl_lock first (when calling unregister_netdev) and then tries to take the sys/fs lock. Deadlock a->b, b->a. The problem starts when ipoib_set_mod frees it's rtnl_lck and tries to get it after that. set_mod: [] ? check_preempt_curr+0x6d/0x90 [] __mutex_lock_slowpath+0x13e/0x180 [] ? __rtnl_unlock+0x15/0x20 [] mutex_lock+0x2b/0x50 [] rtnl_lock+0x15/0x20 [] ipoib_set_mode+0x97/0x160 [ib_ipoib] [] set_mode+0x3b/0x80 [ib_ipoib] [] dev_attr_store+0x20/0x30 [] sysfs_write_file+0xe5/0x170 [] vfs_write+0xb8/0x1a0 [] sys_write+0x51/0x90 [] system_call_fastpath+0x16/0x1b rmmod: [] ? put_dec+0x10c/0x110 [] ? number+0x2ee/0x320 [] schedule_timeout+0x215/0x2e0 [] ? vsnprintf+0x484/0x5f0 [] ? string+0x40/0x100 [] wait_for_common+0x123/0x180 [] ? default_wake_function+0x0/0x20 [] ? ifind_fast+0x5e/0xb0 [] wait_for_completion+0x1d/0x20 [] sysfs_addrm_finish+0x228/0x270 [] sysfs_remove_dir+0xa3/0xf0 [] kobject_del+0x16/0x40 [] device_del+0x184/0x1e0 [] netdev_unregister_kobject+0xab/0xc0 [] rollback_registered+0xae/0x130 [] unregister_netdevice+0x22/0x70 [] unregister_netdev+0x1e/0x30 [] ipoib_remove_one+0xe0/0x120 [ib_ipoib] [] ib_unregister_device+0x4f/0x100 [ib_core] [] mlx4_ib_remove+0x41/0x180 [mlx4_ib] [] mlx4_remove_device+0x71/0x90 [mlx4_core] Fixes: 862096a8bbf8 ("IB/ipoib: Add more rtnl_link_ops callbacks") Cc: # v3.6+ Cc: Or Gerlitz Signed-off-by: Feras Daoud Signed-off-by: Erez Shitrit Signed-off-by: Leon Romanovsky --- drivers/infiniband/ulp/ipoib/ipoib_cm.c | 12 +++++++----- drivers/infiniband/ulp/ipoib/ipoib_main.c | 6 ++---- 2 files changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c index 096c4f6..1c7a9a1 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c @@ -1507,12 +1507,14 @@ static ssize_t set_mode(struct device *d, struct device_attribute *attr, ret = ipoib_set_mode(dev, buf); - rtnl_unlock(); - - if (!ret) - return count; + /* The assumption is that the function ipoib_set_mode returned + * with the rtnl held by it, if not the value -EBUSY returned, + * then no need to rtnl_unlock + */ + if (ret != -EBUSY) + rtnl_unlock(); - return ret; + return (!ret || ret == -EBUSY) ? count : ret; } static DEVICE_ATTR(mode, S_IWUSR | S_IRUGO, show_mode, set_mode); diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c index 1787f6b..1090fe2 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c @@ -493,8 +493,7 @@ int ipoib_set_mode(struct net_device *dev, const char *buf) priv->tx_wr.wr.send_flags &= ~IB_SEND_IP_CSUM; ipoib_flush_paths(dev); - rtnl_lock(); - return 0; + return (!rtnl_trylock()) ? -EBUSY : 0; } if (!strcmp(buf, "datagram\n")) { @@ -503,8 +502,7 @@ int ipoib_set_mode(struct net_device *dev, const char *buf) dev_set_mtu(dev, min(priv->mcast_mtu, dev->mtu)); rtnl_unlock(); ipoib_flush_paths(dev); - rtnl_lock(); - return 0; + return (!rtnl_trylock()) ? -EBUSY : 0; } return -EINVAL; -- 2.10.2