Re: [PATCH] x86/boot: Reject truncated acpi_rsdp= values

[Thorsten Blum]

On Thu, Jun 18, 2026 at 07:48:14PM -0700, Borislav Petkov wrote:
> On Fri, Jun 19, 2026 at 03:00:54AM +0200, Thorsten Blum wrote:
> > You can reproduce this with QEMU using the malformed example from
> > before:
> > 
> > 	acpi_rsdp=0x0123456789abcdefx
> 
> I just did: it says
> 
> [    0.000000] Malformed early option 'acpi_rsdp'
> 
> with latest Linus tree without your patch.
> 
> That's because that comes from setup_acpi_rsdp() which calls kstrtoul().
> 
> I doubt you even hit get_cmdline_acpi_rsdp() as that's the decompressor legacy
> path and modern machines boot through the EFI stub like my guest does...

Are you perhaps appending nokaslr?

With the latest Linus tree, defconfig, and CONFIG_MEMORY_HOTREMOVE=y,
this crashes reproducibly for me, but only when KASLR is not disabled:

qemu-system-x86_64 -nographic -no-reboot -kernel arch/x86/boot/bzImage -append "console=ttyS0 acpi_rsdp=0x0123456789abcdefx"