From: David S. Miller Date: Thu, 27 Feb 2020 04:07:26 +0000 (-0800) Subject: Merge branch 'net-fix-sysfs-permssions-when-device-changes-network' X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=ebb4a4bf76f164457184a3f43ebc1552416bc823;p=openwrt%2Fstaging%2Fblogic.git Merge branch 'net-fix-sysfs-permssions-when-device-changes-network' Christian Brauner says: ==================== net: fix sysfs permssions when device changes network /* v7 */ This is v7 with a build warning fixup that slipped past me the last time. It removes to unused variables in sysfs_group_change_owner(). I observed no warning when building just now. /* v6 */ This is v6 with two small fixups. I missed adapting the commit message to reflect the renamed helper for changing the owner of sysfs files and I also forgot to make the new dpm helper static inline. /* v5 */ This is v5 with a small fixup requested by Rafael. /* v4 */ This is v4 with more documentation and other fixes that Greg requested. /* v3 */ This is v3 with explicit uid and gid parameters added to functions that change sysfs object ownership as Greg requested. (I've tagged this with net-next since it's triggered by a bug for network device files but it also touches driver core aspects so it's not clear-cut. I can of course split this series into separate patchsets.) We have been struggling with a bug surrounding the ownership of network device sysfs files when moving network devices between network namespaces owned by different user namespaces reported by multiple users. Currently, when moving network devices between network namespaces the ownership of the corresponding sysfs entries is not changed. This leads to problems when tools try to operate on the corresponding sysfs files. I also causes a bug when creating a network device in a network namespaces owned by a user namespace and moving that network device back to the host network namespaces. Because when a network device is created in a network namespaces it will be owned by the root user of the user namespace and all its associated sysfs files will also be owned by the root user of the corresponding user namespace. If such a network device has to be moved back to the host network namespace the permissions will still be set to the root user of the owning user namespaces of the originating network namespace. This means unprivileged users can e.g. re-trigger uevents for such incorrectly owned devices on the host or in other network namespaces. They can also modify the settings of the device itself through sysfs when they wouldn't be able to do the same through netlink. Both of these things are unwanted. For example, quite a few workloads will create network devices in the host network namespace. Other tools will then proceed to move such devices between network namespaces owner by other user namespaces. While the ownership of the device itself is updated in net/core/net-sysfs.c:dev_change_net_namespace() the corresponding sysfs entry for the device is not. Below you'll find that moving a network device (here a veth device) from a network namespace into another network namespaces owned by a different user namespace with a different id mapping. As you can see the permissions are wrong even though it is owned by the userns root user after it has been moved and can be interacted with through netlink: drwxr-xr-x 5 nobody nobody 0 Jan 25 18:08 . drwxr-xr-x 9 nobody nobody 0 Jan 25 18:08 .. -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 addr_assign_type -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 addr_len -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 address -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 broadcast -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 carrier -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 carrier_changes -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 carrier_down_count -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 carrier_up_count -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 dev_id -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 dev_port -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 dormant -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 duplex -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 flags -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 gro_flush_timeout -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 ifalias -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 ifindex -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 iflink -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 link_mode -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 mtu -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 name_assign_type -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 netdev_group -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 operstate -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 phys_port_id -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 phys_port_name -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 phys_switch_id drwxr-xr-x 2 nobody nobody 0 Jan 25 18:09 power -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 proto_down drwxr-xr-x 4 nobody nobody 0 Jan 25 18:09 queues -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 speed drwxr-xr-x 2 nobody nobody 0 Jan 25 18:09 statistics lrwxrwxrwx 1 nobody nobody 0 Jan 25 18:08 subsystem -> ../../../../class/net -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:09 tx_queue_len -r--r--r-- 1 nobody nobody 4096 Jan 25 18:09 type -rw-r--r-- 1 nobody nobody 4096 Jan 25 18:08 uevent Constrast this with creating a device of the same type in the network namespace directly. In this case the device's sysfs permissions will be correctly updated. (Please also note, that in a lot of workloads this strategy of creating the network device directly in the network device to workaround this issue can not be used. Either because the network device is dedicated after it has been created or because it used by a process that is heavily sandboxed and couldn't create network devices itself.): drwxr-xr-x 5 root root 0 Jan 25 18:12 . drwxr-xr-x 9 nobody nobody 0 Jan 25 18:08 .. -r--r--r-- 1 root root 4096 Jan 25 18:12 addr_assign_type -r--r--r-- 1 root root 4096 Jan 25 18:12 addr_len -r--r--r-- 1 root root 4096 Jan 25 18:12 address -r--r--r-- 1 root root 4096 Jan 25 18:12 broadcast -rw-r--r-- 1 root root 4096 Jan 25 18:12 carrier -r--r--r-- 1 root root 4096 Jan 25 18:12 carrier_changes -r--r--r-- 1 root root 4096 Jan 25 18:12 carrier_down_count -r--r--r-- 1 root root 4096 Jan 25 18:12 carrier_up_count -r--r--r-- 1 root root 4096 Jan 25 18:12 dev_id -r--r--r-- 1 root root 4096 Jan 25 18:12 dev_port -r--r--r-- 1 root root 4096 Jan 25 18:12 dormant -r--r--r-- 1 root root 4096 Jan 25 18:12 duplex -rw-r--r-- 1 root root 4096 Jan 25 18:12 flags -rw-r--r-- 1 root root 4096 Jan 25 18:12 gro_flush_timeout -rw-r--r-- 1 root root 4096 Jan 25 18:12 ifalias -r--r--r-- 1 root root 4096 Jan 25 18:12 ifindex -r--r--r-- 1 root root 4096 Jan 25 18:12 iflink -r--r--r-- 1 root root 4096 Jan 25 18:12 link_mode -rw-r--r-- 1 root root 4096 Jan 25 18:12 mtu -r--r--r-- 1 root root 4096 Jan 25 18:12 name_assign_type -rw-r--r-- 1 root root 4096 Jan 25 18:12 netdev_group -r--r--r-- 1 root root 4096 Jan 25 18:12 operstate -r--r--r-- 1 root root 4096 Jan 25 18:12 phys_port_id -r--r--r-- 1 root root 4096 Jan 25 18:12 phys_port_name -r--r--r-- 1 root root 4096 Jan 25 18:12 phys_switch_id drwxr-xr-x 2 root root 0 Jan 25 18:12 power -rw-r--r-- 1 root root 4096 Jan 25 18:12 proto_down drwxr-xr-x 4 root root 0 Jan 25 18:12 queues -r--r--r-- 1 root root 4096 Jan 25 18:12 speed drwxr-xr-x 2 root root 0 Jan 25 18:12 statistics lrwxrwxrwx 1 nobody nobody 0 Jan 25 18:12 subsystem -> ../../../../class/net -rw-r--r-- 1 root root 4096 Jan 25 18:12 tx_queue_len -r--r--r-- 1 root root 4096 Jan 25 18:12 type -rw-r--r-- 1 root root 4096 Jan 25 18:12 uevent Now, when creating a network device in a network namespace owned by a user namespace and moving it to the host the permissions will be set to the id that the user namespace root user has been mapped to on the host leading to all sorts of permission issues mentioned above: 458752 drwxr-xr-x 5 458752 458752 0 Jan 25 18:12 . drwxr-xr-x 9 root root 0 Jan 25 18:08 .. -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 addr_assign_type -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 addr_len -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 address -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 broadcast -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 carrier -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 carrier_changes -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 carrier_down_count -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 carrier_up_count -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 dev_id -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 dev_port -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 dormant -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 duplex -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 flags -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 gro_flush_timeout -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 ifalias -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 ifindex -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 iflink -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 link_mode -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 mtu -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 name_assign_type -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 netdev_group -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 operstate -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 phys_port_id -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 phys_port_name -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 phys_switch_id drwxr-xr-x 2 458752 458752 0 Jan 25 18:12 power -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 proto_down drwxr-xr-x 4 458752 458752 0 Jan 25 18:12 queues -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 speed drwxr-xr-x 2 458752 458752 0 Jan 25 18:12 statistics lrwxrwxrwx 1 root root 0 Jan 25 18:12 subsystem -> ../../../../class/net -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 tx_queue_len -r--r--r-- 1 458752 458752 4096 Jan 25 18:12 type -rw-r--r-- 1 458752 458752 4096 Jan 25 18:12 uevent Fix this by changing the basic sysfs files associated with network devices when moving them between network namespaces. To this end we add some infrastructure to sysfs. The patchset takes care to only do this when the owning user namespaces changes and the kids differ. So there's only a performance overhead, when the owning user namespace of the network namespace is different __and__ the kid mappings for the root user are different for the two user namespaces: Assume we have a netdev eth0 which we create in netns1 owned by userns1. userns1 has an id mapping of 0 100000 100000. Now we move eth0 into netns2 which is owned by userns2 which also defines an id mapping of 0 100000 100000. In this case sysfs doesn't need updating. The patch will handle this case and not do any needless work. Now assume eth0 is moved into netns3 which is owned by userns3 which defines an id mapping of 0 123456 65536. In this case the root user in each namespace corresponds to different kid and sysfs needs updating. ==================== Signed-off-by: David S. Miller --- ebb4a4bf76f164457184a3f43ebc1552416bc823