BtrFSītrFS initially developed and designed by Oracle stands for B-Tree File System. Since this file system stopped receiving active support from developers, this paved the way for file systems like BtrFS which could become next big thing in Linux file system world. When first introduced in 2001 and then upgraded in 2004 it was a major competitor to Ext file systems until further development stalled by developers of ReiserFS. It offers compact file allocation and small files along with metadata for preventing using large file system blocks. If you’re looking for a file system which will help you store huge number of small files then ReiserFS is the best alternative file system for you.
Common log file system upgrade#
Ext4 is upgrade to Ext3 and Ext2 file systems and comes with new features such as less fragmentation, larger volumes and files and improved flash memory life with the help of delayed memory allocation.Īs mentioned earlier, Ext4 is one of the most modern file systems and default one in recent Linux and its various distributions. Ext stands for Extended file system and it was first developed especially for Linux and its distributions. There should be no surprise that Ext4 tops the list of best Linux file systems. So today in this article I’m going to give you round-up of best file systems for Linux and its distributions. Data safety and security is so important in this world, so finding the reliable and stable file system for Linux is important to avoid data loss and corruption. Choosing the best file system for Linux and its distributions might be difficult task. BtrFS is still under development and has long road to cover. Many of you might have heard about BtrFS and it becoming default file system for Linux distributions. Reason behind most of the Linux distributions use Ext4 file systems is that it is one of the most stable and flexible file systems out there. Most of the recent Linux distributions use Ext4 file system which is modern and upgraded version of older Ext3 and Ext2 file systems. This can be leveraged to change the size of an adjacent state data object in order to have it overlap with a token when free’d, which can be used to corrupt a process token to privilege escalate.File Systems are very important for every operating system and Linux and its distributions are no exception.
Common log file system free#
In this case, they use the Windows Notification Facility (WNF) and the double free to overlap some state data objects, which they then use to get an out-of-bounds read/write to smash adjacent state data objects. This opens up the possibility to double free, which can be used to poison the pool allocator into granting a targeted use-after-free. The problem is, the shadow block’s pbImage points to the same memory that was just free’d, re-introducing a dangling reference. Just after that free, the record will then be updated and refreshed with the contents from the that block’s mirroring shadow block. By setting up a specially crafted file and getting ExtendMetadataBlockDescriptor() called in the open path, it’s possible to reach a branch that will flush and free a targeted block’s pbImage. Additionally, an attacker also has control over the index of the block to be extended or flushed via the extend context.
Common log file system full#
However, an attacker has full control over the metadata blocks, and can force them to be parsed as extended by manipulating the control record. Under normal circumstances, a stable logfile when being read from the disk will always have an extension state of ClfsExtendStateNone or 0. The eExtendState field is kept track of when operating on a log file. It’s also worth noting that it’s possible for blocks to be “extended” depending on how the control record is setup with it’s various sector offsets. Each of these blocks also has a “shadow block” associated with it, where the metadata is essentially duplicated and backed up for restoration upon an event such as a torn write. Finally, there’s truncate records, which contain info regarding sector changes for truncation ops.
Base records, which have symbol tables and other information like security context info. All Base log files contain 3 different metadata blocks that are parsed when opening log files Control records, which contain layout information and extended area info. Some background is needed on how this custom filesystem works to provide context for the bug. A UAF in the Common Logging File System (CLFS).
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