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Date: Tue, 24 Mar 2020 23:08:18 +0900 From: Taehee Yoo <ap420073@...il.com> To: Greg KH <gregkh@...uxfoundation.org> Cc: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, rafael@...nel.org, j.vosburgh@...il.com, vfalico@...il.com, Andy Gospodarek <andy@...yhouse.net>, Netdev <netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, mitch.a.williams@...el.com Subject: Re: [PATCH net 0/3] net: core: avoid unexpected situation in namespace change routine On Tue, 24 Mar 2020 at 22:28, Greg KH <gregkh@...uxfoundation.org> wrote: > Hi Greg! > On Tue, Mar 24, 2020 at 12:30:41PM +0000, Taehee Yoo wrote: > > This patchset is to avoid an unexpected situation when an interface's > > namespace is being changed. > > > > When interface's namespace is being changed, dev_change_net_namespace() > > is called. This removes and re-allocates many resources that include > > sysfs files. The "/net/class/net/<interface name>" is one of them. > > If the sysfs creation routine(device_rename()) found duplicate sysfs > > file name, it warns about it and fails. But unfortunately, at that point, > > dev_change_net_namespace() doesn't return fail because rollback cost > > is too high. > > So, the interface can't have a sysfs file. > > > > The approach of this patchset is to find the duplicate sysfs file as > > fast as possible. If it found that, dev_change_net_namespace() returns > > fail immediately with zero rollback cost. > > > > 1. The first patch is to add class_find_and_get_file_ns() helper function. > > That function will be used for checking the existence of duplicate > > sysfs file. > > 2. The second patch is to add netdev_class_has_file_ns(). > > That function is to check whether duplicate sysfs file in > > the "/sys/class/net*" using class_find_and_get_file_ns(). > > 3. The last patch is to avoid an unexpected situation. > > a) If duplicate sysfs is existing, it fails as fast as possible in > > the dev_change_net_namespace() > > b) Acquire rtnl_lock() in both bond_create_sysfs() and bond_destroy_sysfs() > > to avoid race condition. > > c) Do not remove "/sys/class/net/bonding_masters" sysfs file by > > bond_destroy_sysfs() if the file wasn't created by bond_create_sysfs(). > > > > Test commands#1: > > ip netns add nst > > ip link add bonding_masters type dummy > > modprobe bonding > > ip link set bonding_masters netns nst > > > > Test commands#2: > > ip link add bonding_masters type dummy > > ls /sys/class/net > > modprobe bonding > > modprobe -rv bonding > > ls /sys/class/net > > > > After removing the bonding module, we can see the "bonding_masters" > > interface's sysfs will be removed. > > This is an unexpected situation. > > > > Taehee Yoo (3): > > class: add class_find_and_get_file_ns() helper function > > net: core: add netdev_class_has_file_ns() helper function > > net: core: avoid warning in dev_change_net_namespace() > > > > drivers/base/class.c | 12 ++++++++++++ > > drivers/net/bonding/bond_sysfs.c | 13 ++++++++++++- > > include/linux/device/class.h | 4 +++- > > include/linux/netdevice.h | 2 +- > > include/net/bonding.h | 1 + > > net/core/dev.c | 4 ++++ > > net/core/net-sysfs.c | 13 +++++++++++++ > > 7 files changed, 46 insertions(+), 3 deletions(-) > > I don't seem to see patch 1/3 anywhere... > I don't know why the first patch was lost. Below is the lkml link. https://lkml.org/lkml/2020/3/24/576 I will resend the first patch. Thank you! Taehee Yoo
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