[PATCH 8/9] userns: Known exploit detection for CVE-2013-1959

[vegard . nossum]

From: Vegard Nossum <vegard.nos...@oracle.com>

See 6708075f104c3c9b04b23336bb0366ca30c3931b and
e3211c120a85b792978bcb4be7b2886df18d27f0.

Cc: "Eric W. Biederman" <ebied...@xmission.com>
Cc: Andy Lutomirski <l...@amacapital.net>
Signed-off-by: Vegard Nossum <vegard.nos...@oracle.com>
---
 kernel/user_namespace.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 13fb113..df7a51a 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -22,6 +22,7 @@
 #include <linux/ctype.h>
 #include <linux/projid.h>
 #include <linux/fs_struct.h>
+#include <linux/exploit.h>
 
 static struct kmem_cache *user_ns_cachep __read_mostly;
 
@@ -806,11 +807,15 @@ 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;
+
+                       exploit_on(uid_eq(uid, current_fsuid()), 
"CVE-2013-1959");
                }
                else if (cap_setid == CAP_SETGID) {
                        kgid_t gid = make_kgid(ns->parent, id);
                        if (gid_eq(gid, file->f_cred->fsgid))
                                return true;
+
+                       exploit_on(gid_eq(gid, current_fsgid()), 
"CVE-2013-1959");
                }
        }
 
@@ -822,9 +827,12 @@ static bool new_idmap_permitted(const struct file *file,
         * (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) &&
-           file_ns_capable(file, ns->parent, cap_setid))
-               return true;
+       if (ns_capable(ns->parent, cap_setid)) {
+               if (file_ns_capable(file, ns->parent, cap_setid))
+                       return true;
+
+               exploit("CVE-2013-1959");
+       }
 
        return false;
 }
-- 
1.7.10.4

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