This is a note to let you know that I've just added the patch titled IB/ipoib: Fix deadlock between rmmod and set_mode to the 4.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ib-ipoib-fix-deadlock-between-rmmod-and-set_mode.patch and it can be found in the queue-4.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 0a0007f28304cb9fc87809c86abb80ec71317f20 Mon Sep 17 00:00:00 2001 From: Feras Daoud <ferasda@xxxxxxxxxxxx> Date: Wed, 28 Dec 2016 14:47:23 +0200 Subject: IB/ipoib: Fix deadlock between rmmod and set_mode From: Feras Daoud <ferasda@xxxxxxxxxxxx> commit 0a0007f28304cb9fc87809c86abb80ec71317f20 upstream. 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: [<ffffffff8104f2bd>] ? check_preempt_curr+0x6d/0x90 [<ffffffff814fee8e>] __mutex_lock_slowpath+0x13e/0x180 [<ffffffff81448655>] ? __rtnl_unlock+0x15/0x20 [<ffffffff814fed2b>] mutex_lock+0x2b/0x50 [<ffffffff81448675>] rtnl_lock+0x15/0x20 [<ffffffffa02ad807>] ipoib_set_mode+0x97/0x160 [ib_ipoib] [<ffffffffa02b5f5b>] set_mode+0x3b/0x80 [ib_ipoib] [<ffffffff8134b840>] dev_attr_store+0x20/0x30 [<ffffffff811f0fe5>] sysfs_write_file+0xe5/0x170 [<ffffffff8117b068>] vfs_write+0xb8/0x1a0 [<ffffffff8117ba81>] sys_write+0x51/0x90 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b rmmod: [<ffffffff81279ffc>] ? put_dec+0x10c/0x110 [<ffffffff8127a2ee>] ? number+0x2ee/0x320 [<ffffffff814fe6a5>] schedule_timeout+0x215/0x2e0 [<ffffffff8127cc04>] ? vsnprintf+0x484/0x5f0 [<ffffffff8127b550>] ? string+0x40/0x100 [<ffffffff814fe323>] wait_for_common+0x123/0x180 [<ffffffff81060250>] ? default_wake_function+0x0/0x20 [<ffffffff8119661e>] ? ifind_fast+0x5e/0xb0 [<ffffffff814fe43d>] wait_for_completion+0x1d/0x20 [<ffffffff811f2e68>] sysfs_addrm_finish+0x228/0x270 [<ffffffff811f2fb3>] sysfs_remove_dir+0xa3/0xf0 [<ffffffff81273f66>] kobject_del+0x16/0x40 [<ffffffff8134cd14>] device_del+0x184/0x1e0 [<ffffffff8144e59b>] netdev_unregister_kobject+0xab/0xc0 [<ffffffff8143c05e>] rollback_registered+0xae/0x130 [<ffffffff8143c102>] unregister_netdevice+0x22/0x70 [<ffffffff8143c16e>] unregister_netdev+0x1e/0x30 [<ffffffffa02a91b0>] ipoib_remove_one+0xe0/0x120 [ib_ipoib] [<ffffffffa01ed95f>] ib_unregister_device+0x4f/0x100 [ib_core] [<ffffffffa021f5e1>] mlx4_ib_remove+0x41/0x180 [mlx4_ib] [<ffffffffa01ab771>] mlx4_remove_device+0x71/0x90 [mlx4_core] Fixes: 862096a8bbf8 ("IB/ipoib: Add more rtnl_link_ops callbacks") Cc: Or Gerlitz <ogerlitz@xxxxxxxxxxxx> Signed-off-by: Feras Daoud <ferasda@xxxxxxxxxxxx> Signed-off-by: Erez Shitrit <erezsh@xxxxxxxxxxxx> Signed-off-by: Leon Romanovsky <leon@xxxxxxxxxx> Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/infiniband/ulp/ipoib/ipoib_cm.c | 12 +++++++----- drivers/infiniband/ulp/ipoib/ipoib_main.c | 6 ++---- 2 files changed, 9 insertions(+), 9 deletions(-) --- 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 ret = ipoib_set_mode(dev, buf); - rtnl_unlock(); + /* 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(); - if (!ret) - return count; - - return ret; + return (!ret || ret == -EBUSY) ? count : ret; } static DEVICE_ATTR(mode, S_IWUSR | S_IRUGO, show_mode, set_mode); --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c @@ -481,8 +481,7 @@ int ipoib_set_mode(struct net_device *de 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")) { @@ -491,8 +490,7 @@ int ipoib_set_mode(struct net_device *de 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; Patches currently in stable-queue which might be from ferasda@xxxxxxxxxxxx are queue-4.10/ib-ipoib-fix-deadlock-between-rmmod-and-set_mode.patch