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

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Date:   Thu, 30 May 2019 13:45:38 +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] kernel/module: Fix mem leak in module_add_modinfo_attrs

+++ YueHaibing [16/05/19 00:12 +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>
>---
> kernel/module.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 0b9aa8a..7da73c4 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -1714,15 +1714,29 @@ 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--) {

I think we need to start at --i.  If sysfs_create_file() returned
an error at index i, we call sysfs_remove_file() starting from the
previously successful call to sysfs_create_file(), i.e. at i - 1.

>+		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;
> }
>
>-- 
>1.8.3.1
>
>