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SubjectRe: [PATCH net 0/3] net: core: avoid unexpected situation in namespace change routine
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...

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