From 5dfb2578b142c3e5cd0c99ba22c8fbc5cf34c81d Mon Sep 17 00:00:00 2001
From: Natalia Portillo <claunia@claunia.com>
Date: Thu, 8 Dec 2022 14:15:24 +0000
Subject: [PATCH] [FAT] Fix that first 2 FAT entries are not considered part of
 the allocation ones, allocating two more.

---
 Aaru.Filesystems/FAT/Info.cs  |  7 ++++---
 Aaru.Filesystems/FAT/Super.cs | 16 ++++++++--------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/Aaru.Filesystems/FAT/Info.cs b/Aaru.Filesystems/FAT/Info.cs
index 219ed2df5..fe05708d1 100644
--- a/Aaru.Filesystems/FAT/Info.cs
+++ b/Aaru.Filesystems/FAT/Info.cs
@@ -710,7 +710,8 @@ namespace Aaru.Filesystems
                 {
                     if(clusters < 4089)
                     {
-                        ushort[] fat12 = new ushort[clusters];
+                        // The first 2 FAT entries do not count as allocation clusters in FAT12 and FAT16
+                        ushort[] fat12 = new ushort[clusters + 2];
 
                         _reservedSectors     = fakeBpb.rsectors;
                         sectorsPerRealSector = fakeBpb.bps / imagePlugin.Info.SectorSize;
@@ -735,7 +736,7 @@ namespace Aaru.Filesystems
                         foreach(ushort entry in fat12)
                         {
                             if(entry >= FAT12_RESERVED ||
-                               entry <= clusters)
+                               entry <= clusters + 2)
                                 continue;
 
                             fat12Valid = false;
@@ -750,7 +751,7 @@ namespace Aaru.Filesystems
                         foreach(ushort entry in fat16)
                         {
                             if(entry >= FAT16_RESERVED ||
-                               entry <= clusters)
+                               entry <= clusters + 2)
                                 continue;
 
                             fat16Valid = false;
diff --git a/Aaru.Filesystems/FAT/Super.cs b/Aaru.Filesystems/FAT/Super.cs
index 3f7c5064b..ce5b30165 100644
--- a/Aaru.Filesystems/FAT/Super.cs
+++ b/Aaru.Filesystems/FAT/Super.cs
@@ -317,7 +317,7 @@ namespace Aaru.Filesystems
                 {
                     if(clusters < 4089)
                     {
-                        ushort[] fat12 = new ushort[clusters];
+                        ushort[] fat12 = new ushort[clusters + 1];
 
                         _reservedSectors     = fakeBpb.rsectors;
                         sectorsPerRealSector = fakeBpb.bps / imagePlugin.Info.SectorSize;
@@ -839,8 +839,8 @@ namespace Aaru.Filesystems
 
             _bytesPerCluster = _sectorsPerCluster * imagePlugin.Info.SectorSize;
 
-            ushort[] firstFatEntries  = new ushort[_statfs.Blocks];
-            ushort[] secondFatEntries = new ushort[_statfs.Blocks];
+            ushort[] firstFatEntries  = new ushort[_statfs.Blocks + 2];
+            ushort[] secondFatEntries = new ushort[_statfs.Blocks + 2];
             bool     firstFatValid    = true;
             bool     secondFatValid   = true;
 
@@ -864,7 +864,7 @@ namespace Aaru.Filesystems
 
                 fatBytes = imagePlugin.ReadSectors(_fatFirstSector + _sectorsPerFat, _sectorsPerFat);
 
-                _fatEntries = new ushort[_statfs.Blocks];
+                _fatEntries = new ushort[_statfs.Blocks + 2];
 
                 pos = 0;
 
@@ -881,7 +881,7 @@ namespace Aaru.Filesystems
                 foreach(ushort entry in firstFatEntries)
                 {
                     if(entry >= FAT12_RESERVED ||
-                       entry <= _statfs.Blocks)
+                       entry <= _statfs.Blocks + 2)
                         continue;
 
                     firstFatValid = false;
@@ -892,7 +892,7 @@ namespace Aaru.Filesystems
                 foreach(ushort entry in secondFatEntries)
                 {
                     if(entry >= FAT12_RESERVED ||
-                       entry <= _statfs.Blocks)
+                       entry <= _statfs.Blocks + 2)
                         continue;
 
                     secondFatValid = false;
@@ -924,7 +924,7 @@ namespace Aaru.Filesystems
                 foreach(ushort entry in firstFatEntries)
                 {
                     if(entry >= FAT16_RESERVED ||
-                       entry <= _statfs.Blocks)
+                       entry <= _statfs.Blocks + 2)
                         continue;
 
                     firstFatValid = false;
@@ -935,7 +935,7 @@ namespace Aaru.Filesystems
                 foreach(ushort entry in secondFatEntries)
                 {
                     if(entry >= FAT16_RESERVED ||
-                       entry <= _statfs.Blocks)
+                       entry <= _statfs.Blocks + 2)
                         continue;
 
                     secondFatValid = false;