From: Eric W. Biederman Date: Sat, 6 Dec 2014 00:14:19 +0000 (-0600) Subject: userns: Don't allow unprivileged creation of gid mappings X-Git-Tag: v3.17.8~25 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7d9436876e6e8b1f9e1e5eeb42a6081e29aadc52;p=thirdparty%2Fkernel%2Fstable.git userns: Don't allow unprivileged creation of gid mappings commit be7c6dba2332cef0677fbabb606e279ae76652c3 upstream. As any gid mapping will allow and must allow for backwards compatibility dropping groups don't allow any gid mappings to be established without CAP_SETGID in the parent user namespace. For a small class of applications this change breaks userspace and removes useful functionality. This small class of applications includes tools/testing/selftests/mount/unprivilged-remount-test.c Most of the removed functionality will be added back with the addition of a one way knob to disable setgroups. Once setgroups is disabled setting the gid_map becomes as safe as setting the uid_map. For more common applications that set the uid_map and the gid_map with privilege this change will have no affect. This is part of a fix for CVE-2014-8989. Reviewed-by: Andy Lutomirski Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 27c8dab48c076..1ce6d67c07b74 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -821,10 +821,6 @@ static bool new_idmap_permitted(const struct file *file, kuid_t uid = make_kuid(ns->parent, id); if (uid_eq(uid, file->f_cred->fsuid)) return true; - } else if (cap_setid == CAP_SETGID) { - kgid_t gid = make_kgid(ns->parent, id); - if (gid_eq(gid, file->f_cred->fsgid)) - return true; } }