linux-kernel - [PATCH] module: fix ddebug_remove

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Date:   Fri, 7 Jul 2017 11:15:58 +0800
From:   Zhou Chengming <zhouchengming1@...wei.com>
To:     <jeyu@...nel.org>, <rusty@...tcorp.com.au>, <jpoimboe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <huawei.libin@...wei.com>,
        <zhouchengming1@...wei.com>
Subject: [PATCH] module: fix ddebug_remove_module()

ddebug_remove_module() use mod->name to find the ddebug_table of the
module and remove it. But dynamic_debug_setup() use the first
_ddebug->modname to create ddebug_table for the module. It's ok when
the _ddebug->modname is the same with the mod->name.

But livepatch module is special, it may contain _ddebugs of other
modules, the modname of which is different from the name of livepatch
module. So ddebug_remove_module() can't use mod->name to find the
right ddebug_table and remove it. It can cause kernel crash when we cat
the file <debugfs>/dynamic_debug/control.

Signed-off-by: Zhou Chengming <zhouchengming1@...wei.com>
---
 kernel/module.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 4a3665f..dac9805 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2703,21 +2703,21 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
 }
 #endif /* CONFIG_KALLSYMS */
 
-static void dynamic_debug_setup(struct _ddebug *debug, unsigned int num)
+static void dynamic_debug_setup(struct module *mod, struct _ddebug *debug, unsigned int num)
 {
 	if (!debug)
 		return;
 #ifdef CONFIG_DYNAMIC_DEBUG
-	if (ddebug_add_module(debug, num, debug->modname))
+	if (ddebug_add_module(debug, num, mod->name))
 		pr_err("dynamic debug error adding module: %s\n",
 			debug->modname);
 #endif
 }
 
-static void dynamic_debug_remove(struct _ddebug *debug)
+static void dynamic_debug_remove(struct module *mod, struct _ddebug *debug)
 {
 	if (debug)
-		ddebug_remove_module(debug->modname);
+		ddebug_remove_module(mod->name);
 }
 
 void * __weak module_alloc(unsigned long size)
@@ -3697,7 +3697,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 		goto free_arch_cleanup;
 	}
 
-	dynamic_debug_setup(info->debug, info->num_debug);
+	dynamic_debug_setup(mod, info->debug, info->num_debug);
 
 	/* Ftrace init must be called in the MODULE_STATE_UNFORMED state */
 	ftrace_module_init(mod);
@@ -3761,7 +3761,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	module_disable_nx(mod);
 
  ddebug_cleanup:
-	dynamic_debug_remove(info->debug);
+	dynamic_debug_remove(mod, info->debug);
 	synchronize_sched();
 	kfree(mod->args);
  free_arch_cleanup:
-- 
1.8.3.1