This sysctl limits groups who can create a new userns without CAP_SYS_ADMIN in the current userns, so as to mitigate potential kernel vulnerabilities around userns. The sysctl value format is same as "net.ipv4.ping_group_range". To disable creating new unprivileged userns, set the sysctl value to "1 0" in the initial userns. To allow everyone to create new userns, set the sysctl value to "0 4294967294". This is the default value. This sysctl replaces "kernel.unprivileged_userns_clone" that is found in Ubuntu [1] and Debian GNU/Linux. Link: https://git.launchpad.net/~ubuntu- kernel/ubuntu/+source/linux/+git/jammy/commit?id=3422764 [1] Signed-off-by: Akihiro Suda <akihiro.suda.cz@xxxxxxxxxxxxx> Akihiro Suda (3): net/ipv4: split group_range logic to kernel/group_range.c group_range: allow GID from 2147483648 to 4294967294 userns: add sysctl "kernel.userns_group_range" include/linux/group_range.h | 18 +++++ include/linux/user_namespace.h | 5 ++ include/net/netns/ipv4.h | 9 +-- include/net/ping.h | 6 -- kernel/Makefile | 2 +- kernel/fork.c | 24 +++++++ kernel/group_range.c | 123 +++++++++++++++++++++++++++++++++ kernel/sysctl.c | 30 ++++++++ kernel/user.c | 9 +++ net/ipv4/ping.c | 39 +---------- net/ipv4/sysctl_net_ipv4.c | 56 ++------------- 11 files changed, 219 insertions(+), 102 deletions(-) create mode 100644 include/linux/group_range.h create mode 100644 kernel/group_range.c -- 2.38.4
