Return -EPERM if an owning user namespace is outside of a process current user namespace.
Signed-off-by: Andrey Vagin <[email protected]> --- include/linux/user_namespace.h | 7 +++++++ kernel/user_namespace.c | 24 ++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index a941b44..e416b76 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -76,6 +76,8 @@ extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, extern ssize_t proc_setgroups_write(struct file *, const char __user *, size_t, loff_t *); extern int proc_setgroups_show(struct seq_file *m, void *v); extern bool userns_may_setgroups(const struct user_namespace *ns); + +struct ns_common *ns_get_owner(struct ns_common *ns); #else static inline struct user_namespace *get_user_ns(struct user_namespace *ns) @@ -104,6 +106,11 @@ static inline bool userns_may_setgroups(const struct user_namespace *ns) { return true; } + +static inline struct ns_common *ns_get_owner(struct ns_common *ns) +{ + return ERR_PTR(-ENOENT); +} #endif #endif /* _LINUX_USER_H */ diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index a5bc78c..6382e5e 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -994,6 +994,30 @@ static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) return commit_creds(cred); } +struct ns_common *ns_get_owner(struct ns_common *ns) +{ + const struct cred *cred = current_cred(); + struct user_namespace *user_ns, *p; + + user_ns = p = ns->user_ns; + if (user_ns == NULL) { /* ns is init_user_ns */ + /* Unprivileged user should not know that it's init_user_ns. */ + if (capable(CAP_SYS_ADMIN)) + return ERR_PTR(-ENOENT); + return ERR_PTR(-EPERM); + } + + for (;;) { + if (p == cred->user_ns) + break; + if (p == &init_user_ns) + return ERR_PTR(-EPERM); + p = p->parent; + } + + return &get_user_ns(user_ns)->ns; +} + const struct proc_ns_operations userns_operations = { .name = "user", .type = CLONE_NEWUSER, -- 2.5.5
