3.8-stable review patch. If anyone has any objections, please let me know.
------------------ From: "Eric W. Biederman" <[email protected]> commit 6708075f104c3c9b04b23336bb0366ca30c3931b upstream. When we require privilege for setting /proc/<pid>/uid_map or /proc/<pid>/gid_map no longer allow an unprivileged user to open the file and pass it to a privileged program to write to the file. Instead when privilege is required require both the opener and the writer to have the necessary capabilities. I have tested this code and verified that setting /proc/<pid>/uid_map fails when an unprivileged user opens the file and a privielged user attempts to set the mapping, that unprivileged users can still map their own id, and that a privileged users can still setup an arbitrary mapping. Reported-by: Andy Lutomirski <[email protected]> Signed-off-by: "Eric W. Biederman" <[email protected]> Signed-off-by: Andy Lutomirski <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/user_namespace.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -25,7 +25,8 @@ static struct kmem_cache *user_ns_cachep __read_mostly; -static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid, +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, struct uid_gid_map *map); static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns) @@ -666,7 +667,7 @@ static ssize_t map_write(struct file *fi ret = -EPERM; /* Validate the user is allowed to use user id's mapped to. */ - if (!new_idmap_permitted(ns, cap_setid, &new_map)) + if (!new_idmap_permitted(file, ns, cap_setid, &new_map)) goto out; /* Map the lower ids from the parent user namespace to the @@ -753,7 +754,8 @@ ssize_t proc_projid_map_write(struct fil &ns->projid_map, &ns->parent->projid_map); } -static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid, +static bool new_idmap_permitted(const struct file *file, + struct user_namespace *ns, int cap_setid, struct uid_gid_map *new_map) { /* Allow mapping to your own filesystem ids */ @@ -777,8 +779,10 @@ static bool new_idmap_permitted(struct u /* Allow the specified ids if we have the appropriate capability * (CAP_SETUID or CAP_SETGID) over the parent user namespace. + * And the opener of the id file also had the approprpiate capability. */ - if (ns_capable(ns->parent, cap_setid)) + if (ns_capable(ns->parent, cap_setid) && + file_ns_capable(file, ns->parent, cap_setid)) return true; return false; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
