1 files changed, 58 insertions, 2 deletions

diff --git a/kernel/static_call.c b/kernel/static_call.c
index 84565c2a41b8..6906c6ec4c97 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -12,6 +12,8 @@
 
 extern struct static_call_site __start_static_call_sites[],
 			       __stop_static_call_sites[];
+extern struct static_call_tramp_key __start_static_call_tramp_key[],
+				    __stop_static_call_tramp_key[];
 
 static bool static_call_initialized;
 
@@ -323,10 +325,59 @@ static int __static_call_mod_text_reserved(void *start, void *end)
 	return ret;
 }
 
+static unsigned long tramp_key_lookup(unsigned long addr)
+{
+	struct static_call_tramp_key *start = __start_static_call_tramp_key;
+	struct static_call_tramp_key *stop = __stop_static_call_tramp_key;
+	struct static_call_tramp_key *tramp_key;
+
+	for (tramp_key = start; tramp_key != stop; tramp_key++) {
+		unsigned long tramp;
+
+		tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp;
+		if (tramp == addr)
+			return (long)tramp_key->key + (long)&tramp_key->key;
+	}
+
+	return 0;
+}
+
 static int static_call_add_module(struct module *mod)
 {
-	return __static_call_init(mod, mod->static_call_sites,
-				  mod->static_call_sites + mod->num_static_call_sites);
+	struct static_call_site *start = mod->static_call_sites;
+	struct static_call_site *stop = start + mod->num_static_call_sites;
+	struct static_call_site *site;
+
+	for (site = start; site != stop; site++) {
+		unsigned long addr = (unsigned long)static_call_key(site);
+		unsigned long key;
+
+		/*
+		 * Is the key is exported, 'addr' points to the key, which
+		 * means modules are allowed to call static_call_update() on
+		 * it.
+		 *
+		 * Otherwise, the key isn't exported, and 'addr' points to the
+		 * trampoline so we need to lookup the key.
+		 *
+		 * We go through this dance to prevent crazy modules from
+		 * abusing sensitive static calls.
+		 */
+		if (!kernel_text_address(addr))
+			continue;
+
+		key = tramp_key_lookup(addr);
+		if (!key) {
+			pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
+				static_call_addr(site));
+			return -EINVAL;
+		}
+
+		site->key = (key - (long)&site->key) |
+			    (site->key & STATIC_CALL_SITE_FLAGS);
+	}
+
+	return __static_call_init(mod, start, stop);
 }
 
 static void static_call_del_module(struct module *mod)
@@ -438,6 +489,11 @@ int __init static_call_init(void)
 }
 early_initcall(static_call_init);
 
+long __static_call_return0(void)
+{
+	return 0;
+}
+
 #ifdef CONFIG_STATIC_CALL_SELFTEST
 
 static int func_a(int x)