linux-kernel - [PATCH v2 5/9] efi: vars: Use locking version to iterate over efivars linked lists

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Message-Id: <20220621153623.3786960-6-ardb@kernel.org>
Date:   Tue, 21 Jun 2022 17:36:19 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-efi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Peter Jones <pjones@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: [PATCH v2 5/9] efi: vars: Use locking version to iterate over efivars linked lists

Both efivars and efivarfs uses __efivar_entry_iter() to go over the
linked list that shadows the list of EFI variables held by the firmware,
but fail to call the begin/end helpers that are documented as a
prerequisite.

So switch to the proper version, which is efivar_entry_iter(). Given
that in both cases, efivar_entry_remove() is invoked with the lock held
already, don't take the lock there anymore.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 drivers/firmware/efi/efivars.c | 8 ++------
 drivers/firmware/efi/vars.c    | 9 +--------
 fs/efivarfs/super.c            | 9 +++------
 include/linux/efi.h            | 2 +-
 4 files changed, 7 insertions(+), 21 deletions(-)

diff --git a/drivers/firmware/efi/efivars.c b/drivers/firmware/efi/efivars.c
index 8341fb15f62e..801a65582172 100644
--- a/drivers/firmware/efi/efivars.c
+++ b/drivers/firmware/efi/efivars.c
@@ -602,10 +602,7 @@ static int efivars_sysfs_callback(efi_char16_t *name, efi_guid_t vendor,
 
 static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
 {
-	int err = efivar_entry_remove(entry);
-
-	if (err)
-		return err;
+	efivar_entry_remove(entry);
 	efivar_unregister(entry);
 	return 0;
 }
@@ -615,8 +612,7 @@ static void efivars_sysfs_exit(void)
 	/* Remove all entries and destroy */
 	int err;
 
-	err = __efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list,
-				  NULL, NULL);
+	err = efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list, NULL);
 	if (err) {
 		pr_err("efivars: Failed to destroy sysfs entries\n");
 		return;
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 5640ffa81544..29540013b358 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -523,17 +523,10 @@ EXPORT_SYMBOL_GPL(__efivar_entry_add);
 /**
  * efivar_entry_remove - remove entry from variable list
  * @entry: entry to remove from list
- *
- * Returns 0 on success, or a kernel error code on failure.
  */
-int efivar_entry_remove(struct efivar_entry *entry)
+void efivar_entry_remove(struct efivar_entry *entry)
 {
-	if (down_interruptible(&efivars_lock))
-		return -EINTR;
 	list_del(&entry->list);
-	up(&efivars_lock);
-
-	return 0;
 }
 EXPORT_SYMBOL_GPL(efivar_entry_remove);
 
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index 09dfa8362f50..6780fc81cc11 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -180,10 +180,7 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 
 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 {
-	int err = efivar_entry_remove(entry);
-
-	if (err)
-		return err;
+	efivar_entry_remove(entry);
 	kfree(entry);
 	return 0;
 }
@@ -219,7 +216,7 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
 	if (err)
-		__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
+		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 
 	return err;
 }
@@ -244,7 +241,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 	kill_litter_super(sb);
 
 	/* Remove all entries and destroy */
-	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
+	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 }
 
 static struct file_system_type efivarfs_type = {
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 08bc6215e3b4..54ca2d6b6c78 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1063,7 +1063,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 
 int efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
 void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
-int efivar_entry_remove(struct efivar_entry *entry);
+void efivar_entry_remove(struct efivar_entry *entry);
 
 int __efivar_entry_delete(struct efivar_entry *entry);
 int efivar_entry_delete(struct efivar_entry *entry);
-- 
2.35.1