Re: [PATCH v3] kernel/module: Fix mem leak in module_add_modinfo_attrs

[Jessica Yu <jeyu@kernel.org>]

+++ YueHaibing [03/06/19 22:45 +0800]:
>In module_add_modinfo_attrs if sysfs_create_file
>fails, we forget to free allocated modinfo_attrs
>and roll back the sysfs files.
>
>Fixes: 03e88ae1b13d ("[PATCH] fix module sysfs files reference counting")
>Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>---
>v3: reuse module_remove_modinfo_attrs
>v2: free from '--i' instead of 'i--'
>---
> kernel/module.c | 21 ++++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 80c7c09..c6b8912 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -1697,6 +1697,8 @@ static int add_usage_links(struct module *mod)
> 	return ret;
> }
>
>+static void module_remove_modinfo_attrs(struct module *mod, int end);
>+
> static int module_add_modinfo_attrs(struct module *mod)
> {
> 	struct module_attribute *attr;
>@@ -1711,24 +1713,33 @@ static int module_add_modinfo_attrs(struct module *mod)
> 		return -ENOMEM;
>
> 	temp_attr = mod->modinfo_attrs;
>-	for (i = 0; (attr = modinfo_attrs[i]) && !error; i++) {
>+	for (i = 0; (attr = modinfo_attrs[i]); i++) {
> 		if (!attr->test || attr->test(mod)) {
> 			memcpy(temp_attr, attr, sizeof(*temp_attr));
> 			sysfs_attr_init(&temp_attr->attr);
> 			error = sysfs_create_file(&mod->mkobj.kobj,
> 					&temp_attr->attr);
>+			if (error)
>+				goto error_out;
> 			++temp_attr;
> 		}
> 	}
>+
>+	return 0;
>+
>+error_out:
>+	module_remove_modinfo_attrs(mod, --i);

Gah, I think there is another issue here - if sysfs_create_file()
fails on the first iteration of the loop (so i = 0), then we will go
to error_out and end up calling module_remove_modinfo_attrs(mod, -1),
which, for i = 0, will call sysfs_remove_file() since attr->attr.name
had already been set before the failed call to sysfs_create_file().
Perhaps we need to check that i > 0 before calling
module_remove_modinfo_attrs() under error_out?

> 	return error;
> }
>
>-static void module_remove_modinfo_attrs(struct module *mod)
>+static void module_remove_modinfo_attrs(struct module *mod, int end)
> {
> 	struct module_attribute *attr;
> 	int i;
>
> 	for (i = 0; (attr = &mod->modinfo_attrs[i]); i++) {
>+		if (end >= 0 && i > end)
>+			break;
> 		/* pick a field to test for end of list */
> 		if (!attr->attr.name)
> 			break;
>@@ -1816,7 +1827,7 @@ static int mod_sysfs_setup(struct module *mod,
> 	return 0;
>
> out_unreg_modinfo_attrs:
>-	module_remove_modinfo_attrs(mod);
>+	module_remove_modinfo_attrs(mod, -1);
> out_unreg_param:
> 	module_param_sysfs_remove(mod);
> out_unreg_holders:
>@@ -1852,7 +1863,7 @@ static void mod_sysfs_fini(struct module *mod)
> {
> }
>
>-static void module_remove_modinfo_attrs(struct module *mod)
>+static void module_remove_modinfo_attrs(struct module *mod, int end)
> {
> }
>
>@@ -1868,7 +1879,7 @@ static void init_param_lock(struct module *mod)
> static void mod_sysfs_teardown(struct module *mod)
> {
> 	del_usage_links(mod);
>-	module_remove_modinfo_attrs(mod);
>+	module_remove_modinfo_attrs(mod, -1);
> 	module_param_sysfs_remove(mod);
> 	kobject_put(mod->mkobj.drivers_dir);
> 	kobject_put(mod->holders_dir);
>-- 
>1.8.3.1
>
>