From d1aa8034d4b287477c80cbe4944008693b8f2f78 Mon Sep 17 00:00:00 2001
From: Piotr Tabor <ptab@google.com>
Date: Sat, 17 Dec 2022 15:48:12 +0100
Subject: [PATCH] Validate page being fetched at possition 'p' self identifies
 as page 'p'. It's the easiest verification whether the page is actually
 written, or its 'random' garbage in the block.

Signed-off-by: Piotr Tabor <ptab@google.com>
---
 page.go | 7 +++++++
 tx.go   | 5 ++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/page.go b/page.go
index c9a158f..e93f627 100644
--- a/page.go
+++ b/page.go
@@ -2,6 +2,7 @@ package bbolt
 
 import (
 	"fmt"
+	"log"
 	"os"
 	"sort"
 	"unsafe"
@@ -53,6 +54,12 @@ func (p *page) meta() *meta {
 	return (*meta)(unsafeAdd(unsafe.Pointer(p), unsafe.Sizeof(*p)))
 }
 
+func (p *page) fastCheck(id pgid) {
+	if p.id != id {
+		log.Panicf("Page expected to be: %v, but self identifies as %v", id, p.id)
+	}
+}
+
 // leafPageElement retrieves the leaf node by index
 func (p *page) leafPageElement(index uint16) *leafPageElement {
 	return (*leafPageElement)(unsafeIndex(unsafe.Pointer(p), unsafe.Sizeof(*p),
diff --git a/tx.go b/tx.go
index 2cc180a..269a18f 100644
--- a/tx.go
+++ b/tx.go
@@ -609,12 +609,15 @@ func (tx *Tx) page(id pgid) *page {
 	// Check the dirty pages first.
 	if tx.pages != nil {
 		if p, ok := tx.pages[id]; ok {
+			p.fastCheck(id)
 			return p
 		}
 	}
 
 	// Otherwise return directly from the mmap.
-	return tx.db.page(id)
+	p := tx.db.page(id)
+	p.fastCheck(id)
+	return p
 }
 
 // forEachPage iterates over every page within a given page and executes a function.