Re: [CFT][PATCH 3/8] userns: Don't allow unprivileged creation of gid mappings
From: Andy Lutomirski <hidden>
Date: 2014-12-09 23:00:50
Also in:
linux-man, lkml, stable
On Tue, Dec 9, 2014 at 12:39 PM, Eric W. Biederman [off-list ref] wrote:
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.
Reviewed-by: Andy Lutomirski <redacted>
quoted hunk ↗ jump to hunk
This is part of a fix for CVE-2014-8989. Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Signed-off-by: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> --- kernel/user_namespace.c | 4 ---- 1 file changed, 4 deletions(-)diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 27c8dab48c07..1ce6d67c07b7 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; } } --1.9.1
-- Andy Lutomirski AMA Capital Management, LLC