livepatch: simplify disable error path

If registering the function with ftrace has previously succeeded,
unregistering will almost never fail.  Even if it does, it's not a fatal
error.  We can still carry on and disable the klp_func from being used
by removing it from the klp_ops func stack.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Reviewed-by: Petr Mladek <pmladek@suse.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 17 insertions, 50 deletions

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index ff7f47d026ac..26df09d56f7c 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -322,32 +322,20 @@ static void notrace klp_ftrace_handler(unsigned long ip,
         klp_arch_set_pc(regs, (unsigned long)func->new_func);
 }
 
-static int klp_disable_func(struct klp_func *func)
+static void klp_disable_func(struct klp_func *func)
 {
         struct klp_ops *ops;
-        int ret;
-
-        if (WARN_ON(func->state != KLP_ENABLED))
-                return -EINVAL;
 
-        if (WARN_ON(!func->old_addr))
-                return -EINVAL;
+        WARN_ON(func->state != KLP_ENABLED);
+        WARN_ON(!func->old_addr);
 
         ops = klp_find_ops(func->old_addr);
         if (WARN_ON(!ops))
-                return -EINVAL;
+                return;
 
         if (list_is_singular(&ops->func_stack)) {
-                ret = unregister_ftrace_function(&ops->fops);
-                if (ret) {
-                        pr_err("failed to unregister ftrace handler for function '%s' (%d)\n",
-                               func->old_name, ret);
-                        return ret;
-                }
-
-                ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
-                if (ret)
-                        pr_warn("function unregister succeeded but failed to clear the filter\n");
+                WARN_ON(unregister_ftrace_function(&ops->fops));
+                WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
 
                 list_del_rcu(&func->stack_node);
                 list_del(&ops->node);
@@ -357,8 +345,6 @@ static int klp_disable_func(struct klp_func *func)
         }
 
         func->state = KLP_DISABLED;
-
-        return 0;
 }
 
 static int klp_enable_func(struct klp_func *func)
@@ -419,23 +405,15 @@ err:
         return ret;
 }
 
-static int klp_disable_object(struct klp_object *obj)
+static void klp_disable_object(struct klp_object *obj)
 {
         struct klp_func *func;
-        int ret;
 
-        for (func = obj->funcs; func->old_name; func++) {
-                if (func->state != KLP_ENABLED)
-                        continue;
-
-                ret = klp_disable_func(func);
-                if (ret)
-                        return ret;
-        }
+        for (func = obj->funcs; func->old_name; func++)
+                if (func->state == KLP_ENABLED)
+                        klp_disable_func(func);
 
         obj->state = KLP_DISABLED;
-
-        return 0;
 }
 
 static int klp_enable_object(struct klp_object *obj)
@@ -451,22 +429,19 @@ static int klp_enable_object(struct klp_object *obj)
 
         for (func = obj->funcs; func->old_name; func++) {
                 ret = klp_enable_func(func);
-                if (ret)
-                        goto unregister;
+                if (ret) {
+                        klp_disable_object(obj);
+                        return ret;
+                }
         }
         obj->state = KLP_ENABLED;
 
         return 0;
-
-unregister:
-        WARN_ON(klp_disable_object(obj));
-        return ret;
 }
 
 static int __klp_disable_patch(struct klp_patch *patch)
 {
         struct klp_object *obj;
-        int ret;
 
         /* enforce stacking: only the last enabled patch can be disabled */
         if (!list_is_last(&patch->list, &klp_patches) &&
@@ -476,12 +451,8 @@ static int __klp_disable_patch(struct klp_patch *patch)
         pr_notice("disabling patch '%s'\n", patch->mod->name);
 
         for (obj = patch->objs; obj->funcs; obj++) {
-                if (obj->state != KLP_ENABLED)
-                        continue;
-
-                ret = klp_disable_object(obj);
-                if (ret)
-                        return ret;
+                if (obj->state == KLP_ENABLED)
+                        klp_disable_object(obj);
         }
 
         patch->state = KLP_DISABLED;
@@ -931,7 +902,6 @@ static void klp_module_notify_going(struct klp_patch *patch,
 {
         struct module *pmod = patch->mod;
         struct module *mod = obj->mod;
-        int ret;
 
         if (patch->state == KLP_DISABLED)
                 goto disabled;
@@ -939,10 +909,7 @@ static void klp_module_notify_going(struct klp_patch *patch,
         pr_notice("reverting patch '%s' on unloading module '%s'\n",
                   pmod->name, mod->name);
 
-        ret = klp_disable_object(obj);
-        if (ret)
-                pr_warn("failed to revert patch '%s' on module '%s' (%d)\n",
-                        pmod->name, mod->name, ret);
+        klp_disable_object(obj);
 
 disabled:
         klp_free_object_loaded(obj);