From 78711524b75955052f240f50a398a1ee53bd2226 Mon Sep 17 00:00:00 2001
From: zensan <sanjos100@gmail.com>
Date: Wed, 30 Mar 2016 23:05:22 +0530
Subject: [PATCH] In all the places where log records are read, there was a
 check that record.size() should not be less than 12.

This "magic number" seems to be the WriteBatch header (8 byte sequence
and 4 byte count).   Replaced all the places where "12" was used
by WriteBatchInternal::kHeader.
---
 db/db_impl.cc              | 2 +-
 db/repair.cc               | 2 +-
 db/transaction_log_impl.cc | 4 ++--
 db/wal_manager.cc          | 2 +-
 db/write_batch.cc          | 6 ++----
 db/write_batch_internal.h  | 4 ++++
 tools/ldb_cmd.cc           | 2 +-
 7 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/db/db_impl.cc b/db/db_impl.cc
index 05051032e4..6124313b86 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -1186,7 +1186,7 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
         continue_replay_log &&
         reader.ReadRecord(&record, &scratch, db_options_.wal_recovery_mode) &&
         status.ok()) {
-      if (record.size() < 12) {
+      if (record.size() < WriteBatchInternal::kHeader) {
         reporter.Corruption(record.size(),
                             Status::Corruption("log record too small"));
         continue;
diff --git a/db/repair.cc b/db/repair.cc
index 6aa72f792c..1681fd5858 100644
--- a/db/repair.cc
+++ b/db/repair.cc
@@ -265,7 +265,7 @@ class Repairer {
     mem->Ref();
     int counter = 0;
     while (reader.ReadRecord(&record, &scratch)) {
-      if (record.size() < 12) {
+      if (record.size() < WriteBatchInternal::kHeader) {
         reporter.Corruption(
             record.size(), Status::Corruption("log record too small"));
         continue;
diff --git a/db/transaction_log_impl.cc b/db/transaction_log_impl.cc
index 624a3af992..8002d935fe 100644
--- a/db/transaction_log_impl.cc
+++ b/db/transaction_log_impl.cc
@@ -107,7 +107,7 @@ void TransactionLogIteratorImpl::SeekToStartSequence(
     return;
   }
   while (RestrictedRead(&record, &scratch)) {
-    if (record.size() < 12) {
+    if (record.size() < WriteBatchInternal::kHeader) {
       reporter_.Corruption(
         record.size(), Status::Corruption("very small log record"));
       continue;
@@ -167,7 +167,7 @@ void TransactionLogIteratorImpl::NextImpl(bool internal) {
       currentLogReader_->UnmarkEOF();
     }
     while (RestrictedRead(&record, &scratch)) {
-      if (record.size() < 12) {
+      if (record.size() < WriteBatchInternal::kHeader) {
         reporter_.Corruption(
           record.size(), Status::Corruption("very small log record"));
         continue;
diff --git a/db/wal_manager.cc b/db/wal_manager.cc
index e1d911e6ec..da4f33aab7 100644
--- a/db/wal_manager.cc
+++ b/db/wal_manager.cc
@@ -455,7 +455,7 @@ Status WalManager::ReadFirstLine(const std::string& fname,
 
   if (reader.ReadRecord(&record, &scratch) &&
       (status.ok() || !db_options_.paranoid_checks)) {
-    if (record.size() < 12) {
+    if (record.size() < WriteBatchInternal::kHeader) {
       reporter.Corruption(record.size(),
                           Status::Corruption("log record too small"));
       // TODO read record's till the first no corrupt entry?
diff --git a/db/write_batch.cc b/db/write_batch.cc
index 3742ae6942..4b8f87a5e6 100644
--- a/db/write_batch.cc
+++ b/db/write_batch.cc
@@ -81,8 +81,6 @@ struct BatchContentClassifier : public WriteBatch::Handler {
 
 }  // anon namespace
 
-// WriteBatch header has an 8-byte sequence number followed by a 4-byte count.
-static const size_t kHeader = 12;
 
 struct SavePoint {
   size_t size;  // size of rep_
@@ -96,8 +94,8 @@ struct SavePoints {
 
 WriteBatch::WriteBatch(size_t reserved_bytes)
     : save_points_(nullptr), content_flags_(0), rep_() {
-  rep_.reserve((reserved_bytes > kHeader) ? reserved_bytes : kHeader);
-  rep_.resize(kHeader);
+  rep_.reserve((reserved_bytes > WriteBatchInternal::kHeader) ? reserved_bytes : WriteBatchInternal::kHeader);
+  rep_.resize(WriteBatchInternal::kHeader);
 }
 
 WriteBatch::WriteBatch(const std::string& rep)
diff --git a/db/write_batch_internal.h b/db/write_batch_internal.h
index 1e7f61e692..3987645ef0 100644
--- a/db/write_batch_internal.h
+++ b/db/write_batch_internal.h
@@ -63,6 +63,10 @@ class ColumnFamilyMemTablesDefault : public ColumnFamilyMemTables {
 // WriteBatch that we don't want in the public WriteBatch interface.
 class WriteBatchInternal {
  public:
+
+  // WriteBatch header has an 8-byte sequence number followed by a 4-byte count.
+  static const size_t kHeader = 12;
+
   // WriteBatch methods with column_family_id instead of ColumnFamilyHandle*
   static void Put(WriteBatch* batch, uint32_t column_family_id,
                   const Slice& key, const Slice& value);
diff --git a/tools/ldb_cmd.cc b/tools/ldb_cmd.cc
index be743955d7..2f4c3e2ad0 100644
--- a/tools/ldb_cmd.cc
+++ b/tools/ldb_cmd.cc
@@ -1576,7 +1576,7 @@ void DumpWalFile(std::string wal_file, bool print_header, bool print_values,
     }
     while (reader.ReadRecord(&record, &scratch)) {
       row.str("");
-      if (record.size() < 12) {
+      if (record.size() < WriteBatchInternal::kHeader) {
         reporter.Corruption(record.size(),
                             Status::Corruption("log record too small"));
       } else {