livepatch/x86: check active func in consistency stack checking

hulk inclusion
category: bugfix
bugzilla: 5507/31358
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: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-By: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

arch/x86/kernel/livepatch.c

@@ -70,6 +70,40 @@ void arch_klp_init_object_loaded(struct klp_patch *patch,
 
 
 #ifdef	CONFIG_LIVEPATCH_WO_FTRACE
+#include <linux/slab.h>
+#include <asm/nops.h>
+#include <asm/sections.h>
+
+#define	JMP_E9_INSN_SIZE	5
+union klp_code_union {
+	char code[JMP_E9_INSN_SIZE];
+	struct {
+		unsigned char e9;
+		int offset;
+	} __packed;
+};
+
+struct klp_func_node {
+	struct list_head node;
+	struct list_head func_stack;
+	unsigned long old_addr;
+	unsigned char old_code[JMP_E9_INSN_SIZE];
+};
+
+static LIST_HEAD(klp_func_list);
+
+static struct klp_func_node *klp_find_func_node(unsigned long old_addr)
+{
+	struct klp_func_node *func_node;
+
+	list_for_each_entry(func_node, &klp_func_list, node) {
+		if (func_node->old_addr == old_addr)
+			return func_node;
+	}
+
+	return NULL;
+}
+
 static inline int klp_compare_address(unsigned long stack_addr,
 		unsigned long func_addr, unsigned long func_size,
 		const char *func_name)
@@ -81,11 +115,14 @@ static inline int klp_compare_address(unsigned long stack_addr,
 	return 0;
 }
 
+static struct klp_func_node *klp_find_func_node(unsigned long old_addr);
+
 static int klp_check_stack_func(struct klp_func *func,
 		struct stack_trace *trace, int enable)
 {
 	unsigned long func_addr, func_size, address;
 	const char *func_name;
+	struct klp_func_node *func_node;
 	int i;
 
 	for (i = 0; i < trace->nr_entries; i++) {
@@ -94,9 +131,33 @@ static int klp_check_stack_func(struct klp_func *func,
 		if (enable) {
 			if (func->force)
 				continue;
-			func_addr = func->old_addr;
-			func_size = func->old_size;
+			/*
+			 * When enable, checking the currently active
+			 * functions.
+			 */
+			func_node = klp_find_func_node(func->old_addr);
+			if (!func_node ||
+			    list_empty(&func_node->func_stack)) {
+				func_addr = func->old_addr;
+				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;
 		}
@@ -188,40 +249,6 @@ int klp_check_calltrace(struct klp_patch *patch, int enable)
 	return ret;
 }
 
-#include <linux/slab.h>
-#include <asm/nops.h>
-#include <asm/sections.h>
-
-#define	JMP_E9_INSN_SIZE	5
-union klp_code_union {
-	char code[JMP_E9_INSN_SIZE];
-	struct {
-		unsigned char e9;
-		int offset;
-	} __packed;
-};
-
-struct klp_func_node {
-	struct list_head node;
-	struct list_head func_stack;
-	unsigned long old_addr;
-	unsigned char old_code[JMP_E9_INSN_SIZE];
-};
-
-static LIST_HEAD(klp_func_list);
-
-static struct klp_func_node *klp_find_func_node(unsigned long old_addr)
-{
-	struct klp_func_node *func_node;
-
-	list_for_each_entry(func_node, &klp_func_list, node) {
-		if (func_node->old_addr == old_addr)
-			return func_node;
-	}
-
-	return NULL;
-}
-
 int arch_klp_init_func(struct klp_object *obj, struct klp_func *func)
 {
 	return 0;