Messages in this thread Patch in this message | | | From | (Eric W. Biederman) | Date | Tue, 09 Dec 2014 14:39:25 -0600 | Subject | [CFT][PATCH 3/8] userns: Don't allow unprivileged creation of gid mappings |
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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.
Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- 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
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