Messages in this thread Patch in this message | | | Date | Fri, 3 Oct 2008 20:37:31 -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 | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-)
4a159b503ed06f6d999b80680538a51ee39d6bd5 diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index d59f193..3fbf520 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -9,6 +9,7 @@ #include <linux/nsproxy.h> #include <linux/slab.h> #include <linux/user_namespace.h> +#include <linux/init_task.h> /* * Clone a new ns copying an original user ns, setting refcount to 1 @@ -47,6 +48,17 @@ int create_new_userns(int flags, struct 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; } -- 1.1.6
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