livepatch/arm: Check active func in consistency stack checking

hulk inclusion
category: bugfix
bugzilla: 51923
CVE: NA

---------------------------

When doing consistency stack checking, if we try to patch a function
which has been patched already. We should check the new function(not
the origin func) that is activeness currently, it's always the first
entry in list func_node->func_stack.

Example :
	module : origin			livepatch v1		livepatch v2
	func   : old func A -[enable]=> new func A' -[enable]=> new func A''
	check  :                A			A'

when we try to patch function A to new function A'' by livepatch v2,
but the func A has already patched to function A' by livepatch v1, so
function A' which provided in livepatch v1 is active in the stack
instead of origin function A. Even if the long jump method is used, we
jump to the new function A' using a call without LR, the origin function
A will not appear in the stack. We must check the active function A' in
consistency stack checking.

Signed-off-by: Cheng Jian <[email protected]>
Reviewed-By: Xie XiuQi <[email protected]>
Signed-off-by: yangerkun <[email protected]>

Signed-off-by: Dong Kai <[email protected]>

Signed-off-by: Ye Weihua <[email protected]>
Reviewed-by: Yang Jihong <[email protected]>
Signed-off-by: Zheng Zengkai <[email protected]>

arch/arm/kernel/livepatch.c

@@ -31,6 +31,41 @@
 #include <asm/insn.h>
 #include <asm/patch.h>
 
+#ifdef CONFIG_ARM_MODULE_PLTS
+#define LJMP_INSN_SIZE	3
+#endif
+
+#ifdef ARM_INSN_SIZE
+#error "ARM_INSN_SIZE have been redefined, please check"
+#else
+#define ARM_INSN_SIZE	4
+#endif
+
+struct klp_func_node {
+	struct list_head node;
+	struct list_head func_stack;
+	void *old_func;
+#ifdef CONFIG_ARM_MODULE_PLTS
+	u32	old_insns[LJMP_INSN_SIZE];
+#else
+	u32	old_insn;
+#endif
+};
+
+static LIST_HEAD(klp_func_list);
+
+static struct klp_func_node *klp_find_func_node(void *old_func)
+{
+	struct klp_func_node *func_node;
+
+	list_for_each_entry(func_node, &klp_func_list, node) {
+		if (func_node->old_func == old_func)
+			return func_node;
+	}
+
+	return NULL;
+}
+
 #ifdef CONFIG_LIVEPATCH_STOP_MACHINE_CONSISTENCY
 struct walk_stackframe_args {
 	struct klp_patch *patch;
@@ -53,6 +88,7 @@ static int klp_check_activeness_func(struct stackframe *frame, void *data)
 	struct walk_stackframe_args *args = data;
 	struct klp_patch *patch = args->patch;
 	struct klp_object *obj;
+	struct klp_func_node *func_node;
 	struct klp_func *func;
 	unsigned long func_addr, func_size;
 	const char *func_name;
@@ -63,9 +99,37 @@ static int klp_check_activeness_func(struct stackframe *frame, void *data)
 	for (obj = patch->objs; obj->funcs; obj++) {
 		for (func = obj->funcs; func->old_name; func++) {
 			if (args->enable) {
-				func_addr = (unsigned long)func->old_func;
-				func_size = func->old_size;
+				/*
+				 * When enable, checking the currently
+				 * active functions.
+				 */
+				func_node = klp_find_func_node(func->old_func);
+				if (!func_node ||
+				    list_empty(&func_node->func_stack)) {
+					/*
+					 * No patched on this function
+					 * [ the origin one ]
+					 */
+					func_addr = (unsigned long)func->old_func;
+					func_size = func->old_size;
+				} else {
+					/*
+					 * Previously patched function
+					 * [ the active one ]
+					 */
+					struct klp_func *prev;
+
+					prev = list_first_or_null_rcu(
+						&func_node->func_stack,
+						struct klp_func, stack_node);
+					func_addr = (unsigned long)prev->new_func;
+					func_size = prev->new_size;
+				}
 			} else {
+				/*
+				 * When disable, check for the function itself
+				 * which to be unpatched.
+				 */
 				func_addr = (unsigned long)func->new_func;
 				func_size = func->new_size;
 			}
@@ -130,41 +194,6 @@ int klp_check_calltrace(struct klp_patch *patch, int enable)
 }
 #endif
 
-#ifdef CONFIG_ARM_MODULE_PLTS
-#define LJMP_INSN_SIZE	3
-#endif
-
-#ifdef ARM_INSN_SIZE
-#error "ARM_INSN_SIZE have been redefined, please check"
-#else
-#define ARM_INSN_SIZE	4
-#endif
-
-struct klp_func_node {
-	struct list_head node;
-	struct list_head func_stack;
-	void *old_func;
-#ifdef CONFIG_ARM_MODULE_PLTS
-	u32	old_insns[LJMP_INSN_SIZE];
-#else
-	u32	old_insn;
-#endif
-};
-
-static LIST_HEAD(klp_func_list);
-
-static struct klp_func_node *klp_find_func_node(void *old_func)
-{
-	struct klp_func_node *func_node;
-
-	list_for_each_entry(func_node, &klp_func_list, node) {
-		if (func_node->old_func == old_func)
-			return func_node;
-	}
-
-	return NULL;
-}
-
 static inline bool offset_in_range(unsigned long pc, unsigned long addr,
 				   long range)
 {