pstore/ram: Should zap persistent zone on unlink

Otherwise, unlinked file will reappear on the next boot.

Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 16ff733..453030f 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -186,6 +186,7 @@
 		return -EINVAL;
 
 	persistent_ram_free_old(cxt->przs[id]);
+	persistent_ram_zap(cxt->przs[id]);
 
 	return 0;
 }