efi-pstore: Fix read iter after pstore API refactor

During the internal pstore API refactoring, the EFI vars read entry was
accidentally made to update a stack variable instead of the pstore
private data pointer. This corrects the problem (and removes the now
needless argument).

Fixes: 125cc42b ("pstore: Replace arguments for read() API")
Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/firmware/efi/efi-pstore.c

@@ -155,19 +155,14 @@ static int efi_pstore_scan_sysfs_exit(struct efivar_entry *pos,
  * efi_pstore_sysfs_entry_iter
  *
  * @record: pstore record to pass to callback
- * @pos: entry to begin iterating from
  *
  * You MUST call efivar_enter_iter_begin() before this function, and
  * efivar_entry_iter_end() afterwards.
  *
- * It is possible to begin iteration from an arbitrary entry within
- * the list by passing @pos. @pos is updated on return to point to
- * the next entry of the last one passed to efi_pstore_read_func().
- * To begin iterating from the beginning of the list @pos must be %NULL.
  */
-static int efi_pstore_sysfs_entry_iter(struct pstore_record *record,
-				       struct efivar_entry **pos)
+static int efi_pstore_sysfs_entry_iter(struct pstore_record *record)
 {
+	struct efivar_entry **pos = (struct efivar_entry **)&record->psi->data;
 	struct efivar_entry *entry, *n;
 	struct list_head *head = &efivar_sysfs_list;
 	int size = 0;
@@ -218,7 +213,6 @@ static int efi_pstore_sysfs_entry_iter(struct pstore_record *record,
  */
 static ssize_t efi_pstore_read(struct pstore_record *record)
 {
-	struct efivar_entry *entry = (struct efivar_entry *)record->psi->data;
 	ssize_t size;
 
 	record->buf = kzalloc(EFIVARS_DATA_SIZE_MAX, GFP_KERNEL);
@@ -229,7 +223,7 @@ static ssize_t efi_pstore_read(struct pstore_record *record)
 		size = -EINTR;
 		goto out;
 	}
-	size = efi_pstore_sysfs_entry_iter(record, &entry);
+	size = efi_pstore_sysfs_entry_iter(record);
 	efivar_entry_iter_end();
 
 out: