Messages in this thread Patch in this message | | | Date | Tue, 26 Aug 2008 13:56:06 -0500 | From | "Serge E. Hallyn" <> | Subject | [PATCH 3/3] user namespaces: reset task's credentials on CLONE_NEWUSER |
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Currently, creating a new user namespace does not reset the task's uid or gid. Since generally that is done as root because it requires CAP_SYS_ADMIN, and since the first uid in the new namespace is 0, one usually doesn't notice. However, if one does
capset cap_sys_admin=ep ns_exec su - hallyn ns_exec -U /bin/sh id
then one will see hallyn's userid, and all preexisting groups.
With this patch, cloning a new user namespace will set the task's uid and gid to 0, and reset the group_info to the empty set assigned to init.
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> --- kernel/user_namespace.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index d59f193..16e6296 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -10,6 +10,9 @@ #include <linux/slab.h> #include <linux/user_namespace.h> +/* defined in kernel/sys.c */ +extern struct group_info init_groups; + /* * Clone a new ns copying an original user ns, setting refcount to 1 * @old_ns: namespace to clone @@ -47,6 +50,17 @@ int create_new_userns(int flags, struct task_struct *tsk) put_user_ns(ns); task_switch_uid(tsk, ns->root_user); + tsk->uid = tsk->euid = tsk->suid = tsk->fsuid = 0; + tsk->gid = tsk->egid = tsk->sgid = tsk->fsgid = 0; + + /* this can't be safe for unshare, can it? it's safe + * for fork, though. I'm tempted to limit clone_newuser to + * fork only */ + task_lock(tsk); + put_group_info(tsk->group_info); + tsk->group_info = &init_groups; + get_group_info(tsk->group_info); + task_unlock(tsk); return 0; } -- 1.5.4.3
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