Linux 4.9 On x86_64 To Support Vmapped Stacks
Written by Michael Larabel in Linux Kernel on 3 October 2016 at 07:15 AM EDT. 13 Comments
LINUX KERNEL --
With the forthcoming Linux 4.9 kernel, x86_64 builds will support CONFIG_VMAP_STACK where kernel stacks are allocated with vmalloc_node for greater security.

Following a lot of work queued for Linux 4.9 and some prep changes merged in earlier 4.8 kernel, Linux on x86_64 will support vmapped stacks by supporting the HAVE_ARCH_VMAP_STACK / CONFIG_VMAP_STACK build-time options. When the option is selected to use virtually-mapped kernel stacks with guard pages, kernel stack overflows are caught immediately as opposed to "difficult-to-diagnose corruption".

The Linux GrSecurity patches previously provided similar functionality via the GRKERNSEC_KSTACKOVERFLOW option. The only downside to this current work is that it doesn't support KASAN (Kernel Address Sanitizer).

With CONFIG_VMAP_STACK enabled there is also an optimization for helping heavy forking workloads.

This vmapped stack work is landing via the x86/asm pull request. Also in there is support for enabling KASLR on vmemmapped memory regions. KASLR, of course, being short for Kernel Address Space Layout Randomization.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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