linux-kernel - Re: [PATCH v2] kernel/module: Fix mem leak in module_add_modinfo

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Date:   Mon, 3 Jun 2019 20:41:32 +0800
From:   Yuehaibing <yuehaibing@...wei.com>
To:     Jessica Yu <jeyu@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
        <paulmck@...ux.ibm.com>
Subject: Re: [PATCH v2] kernel/module: Fix mem leak in
 module_add_modinfo_attrs


On 2019/6/3 18:47, Jessica Yu wrote:
> +++ YueHaibing [30/05/19 21:43 +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@...wei.com>
>> ---
>> v2: free from '--i' instead of 'i--'
>> ---
>> kernel/module.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 6e6712b..78e21a7 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -1723,15 +1723,29 @@ 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:
>> +    for (; (attr = &mod->modinfo_attrs[i]) && i >= 0; --i) {
> 
> The increment step is executed after the body of the loop, so this is
> still starting at i instead of i - 1. I think we need:
> 
>     for (--i; (attr = &mod->modinfo_attrs[i]) && i >= 0; i--)

oops, my bad, will fix it.

> 
> Thanks,
> 
> Jessica
> 
>> +        if (!attr->attr.name)
>> +            break;
>> +        sysfs_remove_file(&mod->mkobj.kobj, &attr->attr);
>> +        if (attr->free)
>> +            attr->free(mod);
>> +    }
>> +    kfree(mod->modinfo_attrs);
>>     return error;
>> }
>>
>> -- 
>> 2.7.4
>>
>>
> 
> .
>