On Wed, Oct 14, 2026 at 07:26:48PM -0500, Iurii Trukhin wrote:
> Since commit f101c5644771 ("arm64: Support ARM64_VA_BITS=52 when
> setting ARCH_MMAP_RND_BITS_MAX"), arm64 supports up to 33, 31, and 29
> bits of mmap ASLR entropy on 48-bit and 52-bit virtual address spaces
> for 4K, 16K, and 64K pages respectively. However, ARCH_MMAP_RND_BITS
> still defaults to ARCH_MMAP_RND_BITS_MIN (18, 16, and 14 bits), which
> was set in commit 8f0d3aa9de57 ("arm64: mm: support ARCH_MMAP_RND_BITS")
> when 39-bit VA was the 4K default.
>
> Set the default ARCH_MMAP_RND_BITS for 48-bit and 52-bit VA to 28 (4K
> pages), 26 (16K pages), and 24 (64K pages), matching x86_64's 1 TiB
> randomization range (5 bits below ARCH_MMAP_RND_BITS_MAX) while keeping
> ARCH_MMAP_RND_BITS_MIN unchanged for smaller VA configurations.
>
> Closes: https://github.com/KSPP/linux/issues/371
> Signed-off-by: Iurii Trukhin <[email protected]>
Yes please. :)
Reviewed-by: Kees Cook <[email protected]>
--
Kees Cook
