[PATCH 2/2] arm64: fix R/O permissions of FDT mapping

Catalin Marinas catalin.marinas at arm.com
Mon Nov 9 06:27:14 PST 2015

On Mon, Nov 09, 2015 at 09:55:46AM +0100, Ard Biesheuvel wrote:
> The mapping permissions of the FDT are set to 'PAGE_KERNEL | PTE_RDONLY'
> in an attempt to map the FDT as read-only. However, not only does this
> break at build time under STRICT_MM_TYPECHECKS (since the two terms are
> of different types in that case), it also results in both the PTE_WRITE
> and PTE_RDONLY attributes to be set, which means the region is still
> writable under ARMv8.1 DBM (and an attempted write will simply clear the
> PT_RDONLY bit).
> So instead, define PAGE_KERNEL_RO (which already has an established
> meaning across architectures) and use that instead.

I guess we don't need cc stable for this, it's only if the kernel has
some other bug that writes the mapped fdt.


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