From: Prarit Bhargava <prarit@redhat.com>
Subject: Re: [RHEL5.1 PATCH] Fix race in efi variable delete code
Date: Fri, 26 Jan 2007 09:54:28 -0500
Bugzilla: 223796
Message-Id: <45BA1624.2040508@redhat.com>
Changelog: Re: [misc] Fix race in efi variable delete code

Fix a race when issuing multiple commands on an efi variable that is
being deleted.

The removal of the variable from the efivars_list should be done immediately
so no other commands can be issued on the variable.

Upstream submit here:

http://marc.theaimsgroup.com/?l=linux-kernel&m=116947959710487&w=2

Resolves BZ 223796.

Successfully tested by me.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>

--- linux-2.6.18.x86_64.orig/drivers/firmware/efivars.c	2007-01-26 09:28:56.000000000 -0500
+++ linux-2.6.18.x86_64/drivers/firmware/efivars.c	2007-01-26 09:41:06.000000000 -0500
@@ -122,8 +122,6 @@ struct efivar_entry {
 	struct kobject kobj;
 };
 
-#define get_efivar_entry(n) list_entry(n, struct efivar_entry, list)
-
 struct efivar_attribute {
 	struct attribute attr;
 	ssize_t (*show) (struct efivar_entry *entry, char *buf);
@@ -386,9 +384,6 @@ static struct sysfs_ops efivar_attr_ops 
 static void efivar_release(struct kobject *kobj)
 {
 	struct efivar_entry *var = container_of(kobj, struct efivar_entry, kobj);
-	spin_lock(&efivars_lock);
-	list_del(&var->list);
-	spin_unlock(&efivars_lock);
 	kfree(var);
 }
 
@@ -430,9 +425,8 @@ static ssize_t
 efivar_create(struct subsystem *sub, const char *buf, size_t count)
 {
 	struct efi_variable *new_var = (struct efi_variable *)buf;
-	struct efivar_entry *search_efivar = NULL;
+	struct efivar_entry *search_efivar, *n;
 	unsigned long strsize1, strsize2;
-	struct list_head *pos, *n;
 	efi_status_t status = EFI_NOT_FOUND;
 	int found = 0;
 
@@ -444,8 +438,7 @@ efivar_create(struct subsystem *sub, con
 	/*
 	 * Does this variable already exist?
 	 */
-	list_for_each_safe(pos, n, &efivar_list) {
-		search_efivar = get_efivar_entry(pos);
+	list_for_each_entry_safe(search_efivar, n, &efivar_list, list) {
 		strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
 		strsize2 = utf8_strsize(new_var->VariableName, 1024);
 		if (strsize1 == strsize2 &&
@@ -490,9 +483,8 @@ static ssize_t
 efivar_delete(struct subsystem *sub, const char *buf, size_t count)
 {
 	struct efi_variable *del_var = (struct efi_variable *)buf;
-	struct efivar_entry *search_efivar = NULL;
+	struct efivar_entry *search_efivar, *n;
 	unsigned long strsize1, strsize2;
-	struct list_head *pos, *n;
 	efi_status_t status = EFI_NOT_FOUND;
 	int found = 0;
 
@@ -504,8 +496,7 @@ efivar_delete(struct subsystem *sub, con
 	/*
 	 * Does this variable already exist?
 	 */
-	list_for_each_safe(pos, n, &efivar_list) {
-		search_efivar = get_efivar_entry(pos);
+	list_for_each_entry_safe(search_efivar, n, &efivar_list, list) {
 		strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
 		strsize2 = utf8_strsize(del_var->VariableName, 1024);
 		if (strsize1 == strsize2 &&
@@ -537,9 +528,9 @@ efivar_delete(struct subsystem *sub, con
 		spin_unlock(&efivars_lock);
 		return -EIO;
 	}
+	list_del(&search_efivar->list);
 	/* We need to release this lock before unregistering. */
 	spin_unlock(&efivars_lock);
-
 	efivar_unregister(search_efivar);
 
 	/* It's dead Jim.... */
@@ -763,10 +754,14 @@ out_free:
 static void __exit
 efivars_exit(void)
 {
-	struct list_head *pos, *n;
+	struct efivar_entry *entry, *n;
 
-	list_for_each_safe(pos, n, &efivar_list)
-		efivar_unregister(get_efivar_entry(pos));
+	list_for_each_entry_safe(entry, n, &efivar_list, list) {
+		spin_lock(&efivars_lock);
+		list_del(&entry->list);
+		spin_unlock(&efivars_lock);
+		efivar_unregister(entry);
+	}
 
 	subsystem_unregister(&vars_subsys);
 	firmware_unregister(&efi_subsys);