Old Linux Kernel Bug Discovered
The bug was introduced back in 2009 and has been lurking around all this time.
Alexander Popov, one of the winners of the 2016 Linux Foundation Training (LiFT) scholarship, has discovered a very old bug in the Linux kernel that can affect modern systems.
Popov wrote on a mailing list, “This is an announcement of CVE-2017-2636, which is a race condition in the n_hdlc Linux kernel driver (drivers/tty/n_hdlc.c). It can be exploited to gain a local privilege escalation. This driver provides HDLC serial line discipline and comes as a kernel module in many Linux distributions, which have CONFIG_N_HDLC=m in the kernel config.”
Popov fixed the issue by using “standard kernel linked list protected by a spinlock and got rid of n_hdlc.tbuf. In the case of transmission error, the current data buffer is put after the head of tx_buf_list,” he wrote on the mailing list.
The issue is affecting major distributions, including Red Hat Enterprise Linux. According to a Red Hat Bugzilla submission, although RHEL 5 is unaffected, the bug does affect the Linux kernel packages shipped with Red Hat Enterprise Linux 6 and 7 and Red Hat Enterprise MRG 2. Because this issue is rated important, it has been scheduled to be fixed in future updates for the respective releases. Canonical has already released a patch; SUSE is working on it.
The bug is old, and the module is used in really old hardware; even if the module is shipped with modern Linux distributions, it’s never loaded by default. However, the module is automatically loaded “if an unprivileged user opens a pseudoterminal and calls TIOCSETD ioctl for it setting N_HDLC line discipline,” explained Popov.
One might wonder why users should worry about it. Steven J. Vaughan-Nichols explained, because “it's easy to do, which means it's easy for a local user to exploit. Before poo-pooing this as a non-issue, keep in mind that with hosted and cloud computing, many people have ‘local’ access to Linux servers.”
As always, check your distribution and run updates to patch the flaws.
Issue 268/2023
Buy this issue as a PDF
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Find SysAdmin Jobs
News
-
Escuelas Linux 8.0 is Now Available
Just in time for its 25th anniversary, the developers of Escuelas Linux have released the latest version.
-
LibreOffice 7.5 has Arrived Loaded with New Features and Improvements
The favorite office suite of the Linux community has a new release that includes some visual refreshing and new features across all modules.
-
The Next Major Release of Elementary OS Has Arrived
It's been over a year since the developers of elementary OS released version 6.1 (Jólnir) but they've finally made their latest release (Horus) available with a renewed focus on the user.
-
KDE Plasma 5.27 Beta Is Ready for Testing
The latest beta iteration of the KDE Plasma desktop is now available and includes some important additions and fixes.
-
Netrunner OS 23 Is Now Available
The latest version of this Linux distribution is now based on Debian Bullseye and is ready for installation and finally hits the KDE 5.20 branch of the desktop.
-
New Linux Distribution Built for Gamers
With a Gnome desktop that offers different layouts and a custom kernel, PikaOS is a great option for gamers of all types.
-
System76 Beefs Up Popular Pangolin Laptop
The darling of open-source-powered laptops and desktops will soon drop a new AMD Ryzen 7-powered version of their popular Pangolin laptop.
-
Nobara Project Is a Modified Version of Fedora with User-Friendly Fixes
If you're looking for a version of Fedora that includes third-party and proprietary packages, look no further than the Nobara Project.
-
Gnome 44 Now Has a Release Date
Gnome 44 will be officially released on March 22, 2023.
-
Nitrux 2.6 Available with Kernel 6.1 and a Major Change
The developers of Nitrux have officially released version 2.6 of their Linux distribution with plenty of new features to excite users.