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

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Message-ID: <20190603104716.GA21759@linux-8ccs>
Date:   Mon, 3 Jun 2019 12:47:16 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     YueHaibing <yuehaibing@...wei.com>
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

+++ 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--)

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
>
>