From 0a0007f28304cb9fc87809c86abb80ec71317f20 Mon Sep 17 00:00:00 2001 From: Feras Daoud Date: Wed, 28 Dec 2016 14:47:23 +0200 Subject: [PATCH] IB/ipoib: Fix deadlock between rmmod and set_mode 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 Signed-off-by: Doug Ledford --- 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 096c4f6fbd65..1c7a9a16efc7 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 cbd06a882a60..045f844d7f4a 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c @@ -492,8 +492,7 @@ 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")) { @@ -502,8 +501,7 @@ 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; -- 2.20.1