1 files changed, 32 insertions, 0 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index 7cd61a5f5205..97ac1f167717 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -28,6 +28,28 @@
 #include <linux/prctl.h>
 #include <linux/securebits.h>
 
+/*
+ * If a non-root user executes a setuid-root binary in
+ * !secure(SECURE_NOROOT) mode, then we raise capabilities.
+ * However if fE is also set, then the intent is for only
+ * the file capabilities to be applied, and the setuid-root
+ * bit is left on either to change the uid (plausible) or
+ * to get full privilege on a kernel without file capabilities
+ * support.  So in that case we do not raise capabilities.
+ *
+ * Warn if that happens, once per boot.
+ */
+static void warn_setuid_and_fcaps_mixed(char *fname)
+{
+        static int warned;
+        if (!warned) {
+                printk(KERN_INFO "warning: `%s' has both setuid-root and"
+                        " effective capabilities. Therefore not raising all"
+                        " capabilities.\n", fname);
+                warned = 1;
+        }
+}
+
 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
 {
         NETLINK_CB(skb).eff_cap = current_cap();
@@ -464,6 +486,15 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
 
         if (!issecure(SECURE_NOROOT)) {
                 /*
+                 * If the legacy file capability is set, then don't set privs
+                 * for a setuid root binary run by a non-root user.  Do set it
+                 * for a root user just to cause least surprise to an admin.
+                 */
+                if (effective && new->uid != 0 && new->euid == 0) {
+                        warn_setuid_and_fcaps_mixed(bprm->filename);
+                        goto skip;
+                }
+                /*
                  * To support inheritance of root-permissions and suid-root
                  * executables under compatibility mode, we override the
                  * capability sets for the file.
@@ -478,6 +509,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
                 if (new->euid == 0)
                         effective = true;
         }
+skip:
 
         /* Don't let someone trace a set[ug]id/setpcap binary with the revised
          * credentials unless they have the appropriate permit