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Kernel: LWN Coverage (No Longer Paywalled) and Initial HDMI 2.0 Support With Nouveau Slated For The Next Linux Kernel

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Linux
  • Revenge of the modems

    Back in the halcyon days of the previous century, those with a technical inclination often became overly acquainted with modems—not just the strange sounds they made when connecting, but the AT commands that were used to control them. While the AT command set is still in use (notably for GSM networks), it is generally hidden these days. But some security researchers have found that Android phones often make AT commands available via their USB ports, which is something that can potentially be exploited by rogue USB devices of various sorts.

    A paper [PDF] that was written by a long list of researchers (Dave (Jing) Tian, Grant Hernandez, Joseph I. Choi, Vanessa Frost, Christie Ruales, Patrick Traynor, Hayawardh Vijayakumar, Lee Harrison, Amir Rahmati, Michael Grace, and Kevin R. B. Butler) and presented at the 27th USENIX Security Symposium described the findings. A rather large number of Android firmware builds were scanned for the presence of AT commands and many were found to have them. That's not entirely surprising since the baseband processors used to communicate with the mobile network often use AT commands for configuration. But it turns out that Android vendors have also added their own custom AT commands that can have a variety of potentially harmful effects—making those available over USB is even more problematic.

    They started by searching through 2018 separate Android binary images (it is not clear how that number came about, perhaps it is simply coincidental) from 11 different vendors. They extracted and decompressed the various pieces inside the images and then searched those files for AT command strings. That process led to a database of 3500 AT commands, which can be seen at the web site for ATtention Spanned—the name given to the vulnerabilities.

  • XFS, LSM, and low-level management APIs

    The Linux Security Module (LSM) subsystem allows security modules to hook into many low-level operations within the kernel; modules can use those hooks to examine each requested operation and decide whether it should be allowed to proceed or not. In theory, just about every low-level operation is covered by an LSM hook; in practice, there are some gaps. A discussion regarding one of those gaps — low-level ioctl() operations on XFS filesystems — has revealed a thorny problem and a significant difference of opinion on what the correct solution is.

    In late September Tong Zhang pointed out that xfs_file_ioctl(), the 300-line function that dispatches the various ioctl() operations that can be performed on an XFS filesystem, was making a call to vfs_readlink() without first consulting the security_inode_readlink() LSM hook. As a result, a user with the privilege to invoke that operation (CAP_SYS_ADMIN) could read the value of a symbolic link within the filesystem, even if the security policy in place would otherwise forbid it. Zhang suggested that a call to the LSM hook should be added to address this problem.

  • Initial HDMI 2.0 Support With Nouveau Slated For The Next Linux Kernel

    Days after Nouveau DRM maintainer Ben Skeggs began staging changes for this open-source NVIDIA driver ahead of the next kernel cycle, this evening Ben Skeggs submitted the DRM-Next pull request to queue this work for the Linux 4.20/5.0 kernel cycle.

    As covered in that previous article, there isn't a whole lot on the Nouveau kernel driver front at this time. Skeggs summed up these open-source NVIDIA driver changes as: "Just initial HDMI 2.0 support, and a bunch of other cleanups."

  • Device-to-device memory-transfer offload with P2PDMA

    One of the most common tasks carried out by device drivers is setting up DMA operations for data transfers between main memory and the device. Often, data read into memory from one device will be immediately written, unchanged, to another device. Common examples include carrying the image between the camera and screen on a mobile phone, or downloading files to be saved on a disk. Those transfers have an impact on the CPU even if it does not use the data directly, due to higher memory use and effects like cache trashing. There are cases where it is possible to avoid usage of the system memory completely, though. A patch set (posted by Logan Gunthorpe with contributions by Christoph Hellwig and Steve Wise) has been in the works for some time that addresses this case for PCI devices using peer-to-peer (P2P) transfers, with a focus on offering an offload option for the NVMe fabrics target subsystem.

More in Tux Machines

Opening Files with Qt on Android

After addressing Android support in KF5Notifications another fairly generic task that so far required Android specific code is next: opening files. Due to the security isolation of apps and the way the native “file dialog” works on Android this is quite different from other platforms, which makes application code a bit ugly. This can be fixed in Qt though. Read more

Android Leftovers

Ubuntu-Centric Full Circle Magazine and Debian on the Raspberryscape

  • Full Circle Magazine: Full Circle Weekly News #121
  • Debian on the Raspberryscape: Great news!
    I already mentioned here having adopted and updated the Raspberry Pi 3 Debian Buster Unofficial Preview image generation project. As you might know, the hardware differences between the three families are quite deep ? The original Raspberry Pi (models A and B), as well as the Zero and Zero W, are ARMv6 (which, in Debian-speak, belong to the armel architecture, a.k.a. EABI / Embedded ABI). Raspberry Pi 2 is an ARMv7 (so, we call it armhf or ARM hard-float, as it does support floating point instructions). Finally, the Raspberry Pi 3 is an ARMv8-A (in Debian it corresponds to the ARM64 architecture). [...] As for the little guy, the Zero that sits atop them, I only have to upload a new version of raspberry3-firmware built also for armel. I will add to it the needed devicetree files. I have to check with the release-team members if it would be possible to rename the package to simply raspberry-firmware (as it's no longer v3-specific). Why is this relevant? Well, the Raspberry Pi is by far the most popular ARM machine ever. It is a board people love playing with. It is the base for many, many, many projects. And now, finally, it can run with straight Debian! And, of course, if you don't trust me providing clean images, you can prepare them by yourself, trusting the same distribution you have come to trust and love over the years.

OSS: SVT-AV1, LibreOffice, FSF and Software Freedom Conservancy

  • SVT-AV1 Already Seeing Nice Performance Improvements Since Open-Sourcing
    It was just a few weeks ago that Intel open-sourced the SVT-AV1 project as a CPU-based AV1 video encoder. In the short time since publishing it, there's already been some significant performance improvements.  Since the start of the month, SVT-AV1 has added multi-threaded CDEF search, more AVX optimizations, and other improvements to this fast evolving AV1 encoder. With having updated the test profile against the latest state as of today, here's a quick look at the performance of this Intel open-source AV1 video encoder.
  • Find a LibreOffice community member near you!
    Hundreds of people around the world contribute to each new version of LibreOffice, and we’ve interviewed many of them on this blog. Now we’ve collected them together on a map (thanks to OpenStreetMap), so you can see who’s near you, and find out more!
  • What I learned during my internship with the FSF tech team
    Hello everyone, I am Hrishikesh, and this is my follow-up blog post concluding my experiences and the work I did during my 3.5 month remote internship with the FSF. During my internship, I worked with the tech team to research and propose replacements for their network monitoring infrastructure. A few things did not go quite as planned, but a lot of good things that I did not plan happened along the way. For example, I planned to work on GNU LibreJS, but never could find enough time for it. On the other hand, I gained a lot of system administration experience by reading IRC conversations, and by working on my project. I even got to have a brief conversation with RMS! My mentors, Ian, Andrew, and Ruben, were extremely helpful and understanding throughout my internship. As someone who previously had not worked with a team, I learned a lot about teamwork. Aside from IRC, we interacted weekly in a conference call via phone, and used the FSF's Etherpad instance for live collaborative editing, to take notes. The first two months were mostly spent studying the FSF's existing Nagios- and Munin-based monitoring and alert system, to understand how it works. The tech team provided two VMs for experimenting with Prometheus and Nagios, which I used throughout the internship. During this time, I also spent a lot of time reading about licenses, and other posts about free software published by the FSF.
  • We're Hiring: Techie Bookkeeper
    Software Freedom Conservancy is looking for a new employee to help us with important work that supports our basic operations. Conservancy is a nonprofit charity that promotes and improves free and open source software projects. We are home to almost 50 projects, including Git, Inkscape, Etherpad, phpMyAdmin, and Selenium (to name a few). Conservancy is the home of Outreachy, an award winning diversity intiative, and we also work hard to improve software freedom generally. We are a small but dedicated staff, handling a very large number of financial transactions per year for us and our member projects.