From a403df438598f76459249dd3ceda957ce44b1bb5 Mon Sep 17 00:00:00 2001 From: Floris Bos Date: Sun, 20 Nov 2022 18:44:22 +0100 Subject: [PATCH] Advanced settings FAT modification: fix expanding directory When no more directory entries are available in the existing cluster(s) of a directory on FAT32, we allocate an extra cluster. Make sure to zero out that new cluster, as disk checking utilities may not stop reading when reaching an end of directory marker but read the rest of cluster as well. So there must not be any garbage data from a previously deleted file in the sector there. Also add checks to prevent getting in an endless loop on encoutering circular "next cluster" references. --- debian/changelog | 2 +- src/devicewrapperfatpartition.cpp | 25 ++++++++++++++++++++++--- src/devicewrapperfatpartition.h | 1 + 3 files changed, 24 insertions(+), 4 deletions(-) diff --git a/debian/changelog b/debian/changelog index 53878de..92881b9 100644 --- a/debian/changelog +++ b/debian/changelog @@ -8,7 +8,7 @@ rpi-imager (1.7.4) unstable; urgency=medium disk device, without having to rely on the operating system to mount the partition first. - -- Floris Bos Mon, 14 Nov 2022 21:49:27 +0100 + -- Floris Bos Sun, 20 Nov 2022 17:30:20 +0100 rpi-imager (1.7.3) unstable; urgency=medium diff --git a/src/devicewrapperfatpartition.cpp b/src/devicewrapperfatpartition.cpp index cd5e1c5..a05d2c4 100644 --- a/src/devicewrapperfatpartition.cpp +++ b/src/devicewrapperfatpartition.cpp @@ -506,6 +506,8 @@ void DeviceWrapperFatPartition::updateDirEntry(struct dir_entry *dirEntry) struct dir_entry iterEntry; openDir(); + quint64 oldOffset = _offset; + while (readDir(&iterEntry)) { /* Look for existing entry with same short filename */ @@ -513,10 +515,12 @@ void DeviceWrapperFatPartition::updateDirEntry(struct dir_entry *dirEntry) && memcmp(dirEntry->DIR_Name, iterEntry.DIR_Name, sizeof(iterEntry.DIR_Name)) == 0) { /* seek() back and write out new entry */ - _offset -= sizeof(*dirEntry); + _offset = oldOffset; write((char *) dirEntry, sizeof(*dirEntry)); return; } + + oldOffset = _offset; } throw std::runtime_error("Error locating existing directory entry"); @@ -524,6 +528,7 @@ void DeviceWrapperFatPartition::updateDirEntry(struct dir_entry *dirEntry) void DeviceWrapperFatPartition::writeDirEntryAtCurrentPos(struct dir_entry *dirEntry) { + //qDebug() << "Write new entry" << QByteArray((char *) dirEntry->DIR_Name, 11); write((char *) dirEntry, sizeof(*dirEntry)); if (_type == FAT32) @@ -532,15 +537,23 @@ void DeviceWrapperFatPartition::writeDirEntryAtCurrentPos(struct dir_entry *dirE { /* We reached the end of the cluster, allocate/seek to next cluster */ uint32_t nextCluster = getFAT(_fat32_currentRootDirCluster); - /* FIXME: should we check for circular cluster references? */ if (nextCluster > 0xFFFFFF7) { nextCluster = allocateCluster(_fat32_currentRootDirCluster); } + if (_currentDirClusters.contains(nextCluster)) + throw std::runtime_error("Circular cluster references in FAT32 directory detected"); + _currentDirClusters.append(nextCluster); + _fat32_currentRootDirCluster = nextCluster; seekCluster(_fat32_currentRootDirCluster); + + /* Zero out entire new cluster, as fsck.fat does not stop reading entries at end-of-directory marker */ + QByteArray zeroes(_bytesPerCluster, 0); + write(zeroes.data(), zeroes.length() ); + seekCluster(_fat32_currentRootDirCluster); } } else if (pos() > (_fat16_firstRootDirSector+_fat16_rootDirSectors)*_bytesPerSector) @@ -560,6 +573,10 @@ void DeviceWrapperFatPartition::openDir() { _fat32_currentRootDirCluster = _fat32_firstRootDirCluster; seekCluster(_fat32_currentRootDirCluster); + /* Keep track of directory clusters we seeked to, to be able + to detect circular references */ + _currentDirClusters.clear(); + _currentDirClusters.append(_fat32_currentRootDirCluster); } } @@ -581,11 +598,13 @@ bool DeviceWrapperFatPartition::readDir(struct dir_entry *result) { /* We reached the end of the cluster, seek to next cluster */ uint32_t nextCluster = getFAT(_fat32_currentRootDirCluster); - /* FIXME: should we check for circular cluster references? */ if (nextCluster > 0xFFFFFF7) throw std::runtime_error("Reached end of FAT32 root directory, but no end-of-directory marker found"); + if (_currentDirClusters.contains(nextCluster)) + throw std::runtime_error("Circular cluster references in FAT32 directory detected"); + _currentDirClusters.append(nextCluster); _fat32_currentRootDirCluster = nextCluster; seekCluster(_fat32_currentRootDirCluster); } diff --git a/src/devicewrapperfatpartition.h b/src/devicewrapperfatpartition.h index ed22afc..0c7496b 100644 --- a/src/devicewrapperfatpartition.h +++ b/src/devicewrapperfatpartition.h @@ -31,6 +31,7 @@ protected: uint32_t _fat32_firstRootDirCluster, _fat32_currentRootDirCluster; uint16_t _bytesPerSector, _fat32_fsinfoSector; QList _fatStartOffset; + QList _currentDirClusters; QList getClusterChain(uint32_t firstCluster); void setFAT16(uint16_t cluster, uint16_t value);