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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

Graphics: Mesa, Vega and ETC2

  • RADV Driver Gets Big Patch Series For 8-bit & 16-bit Arithmetic, 8-bit Storage
    A set of 38 patches have been sent out that wire in support for the VK_KHR_shader_float16_int8, VK_AMD_gpu_shader_half_float, VK_AMD_gpu_shader_int16, and VK_KHR_8bit_storage extensions to the RADV driver within Mesa. Rhys Perry who started contributing to the Nouveau driver stack has been working on this 8-bit and 16-bit arithmetic support for the Radeon Vulkan "RADV" driver. These 8-bit / 16-bit extensions work for AMD Volcanic Islands GPUs and newer. However, the half-floats support needs LLVM 8.0 or newer due to bugs on LLVM 7.
  • BACO Power Savings Support Comes To AMD's Vega 12
    The latest addition to AMD's open-source Linux kernel driver is supporting BACO on Vega 12. With the upcoming Linux 5.1 kernel cycle, BACO is enabled for Vega 10 and Vega 20. BACO is short for Bus Active, Chip Off as a low-power mode whereby most of the GPU is shut-off during idle periods in order to drastically cut the power consumption of the graphics card. BACO is also known as AMD ZeroCore Power mode.
  • Improved ETC2 Texture Compression Lands For Older Haswell/Ivybridge GPUs On Linux
    The previously mentioned work on improving ETC2 support for older generations of Intel graphics has now been mainlined for Mesa 19.1. This work for the ETC2 texture compression is improving the "fake" support for Intel Gen 7 class graphics, the Ivybridge and Haswell era graphics. This work was done by Igalia to address the lack of native ETC2 coverage on these several year old chips. Following this improved implementation for the fake ETC2 support is also wiring up OES_copy_image support for this extension. ETC2 is the lossy texture compression mandated since OpenGL ES 3.0 and OpenGL 4.3.

Bitmain SoC Support Coming To Linux 5.1 - Sophon ARMv8 + RISC-V Chip For Deep Learning

Queued for mainlining with the upcoming Linux 5.1 kernel cycle is initial support for Bitmain SoCs. Bitmain is the Chinese company that started out designing ASICs for Bitcoin mining with the Antminer and other products. The company has also been venturing into designs for artificial intelligence and deep learning. With the upcoming Linux 5.1 kernel will be initial support for Bitmain's BM1880 System-on-a-Chip as well as the "Sophon Edge" developer board. Read more

Debian Developers' Updates and Python Bits

Tales of colours: GIMP and Latte Dock (KDE)

  • Colorization in GIMP
    As part of the Image team at GREYC lab (CRNS, ENSICAEN, University of Caen), I implemented the “fill by line art” algorithm in GIMP, also known as “Smart Colorization“. You may know this algorithm in G’Mic (developed by the same team), so when they proposed me to work with them, I wanted to implement this algorithm in GIMP core. Thus it became my first assignment.
  • Latte and a Colors tale...
    A few months ago while I was scratching Latte Dock limits an idea came and haunted my thoughts. How Latte could give the colors freedom for panels and windows that an Android phone already provides? Questions like this arose and solutions appeared suddenly in many different places, but an important and concrete dream prevail in the end.