linux-kernel - Re: [PATCH 0/2] Map initrd as encrypted when relocating if SME is enabled

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Message-ID: <763b73a4-55b6-2cd3-02e9-1086d36cf270@amd.com>
Date:   Thu, 24 Nov 2022 08:26:38 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Zelin Deng <zelin.deng@...ux.alibaba.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 0/2] Map initrd as encrypted when relocating if SME is
 enabled

On 11/24/22 03:12, Zelin Deng wrote:
> I found an issue on SME enabled AMD machine when initrd is relocated if
> it was located in e820 reserved area.
> For example key dmesg output:
> ...
> [mem 0x000000005aafe000-0x000000006005ffff] reserved //e820 mapping
> Move RAMDISK from [mem 0x5aafe000-0x5ccd5167] //relocate_initrd()
> ...
> 
> Early initrd will be copied by copy_from_early_mem() which will clear
> encrypted pgprot flag as initrd source address is not in kernel usable
> area. As initrd has been encrypted at earlier stage, encrypted data is
> copied, which leads new initrd cannot be unpacked, then rootfs cannot be
> mounted.

This is actually a bug in Grub where the kernel and initrd was moved out 
of loader_code/data and into runtime_service_code/data. This commit has 
since been reverted because it goes against the UEFI specification. It was 
a small window, but the bad version was picked up by some distros. No need 
for a kernel change, please update your version of Grub.

Thanks,
Tom

> dmesg output:
> ...
> [   11.296725] Trying to unpack rootfs image as initramfs...
> [   11.302127] Initramfs unpacking failed: invalid magic at start of compressed archive
> ...
> [   16.698152] /dev/root: Can't open blockdev
> [   16.702255] VFS: Cannot open root device "PARTUUID=0ad58d87-05c7-43f8-b147-93140ad315e5" or unknown-block(0,0): error -6
> [   16.713114] Please append a correct "root=" boot option; here are the available partitions:
> [   16.721462] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
> [   16.729716] CPU: 9 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc5-next-20221114 #3
> [   16.737099] Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM1008B 01/19/2022
> [   16.745175] Call Trace:
> [   16.747623]  <TASK>
> [   16.749727]  dump_stack_lvl+0x38/0x4c
> [   16.753393]  panic+0xfb/0x28a
> [   16.771999]  ? _printk+0x4c/0x52
> [   16.775224]  mount_block_root+0x143/0x1dd
> [   16.779237]  prepare_namespace+0x13f/0x16e
> [   16.783334]  kernel_init_freeable+0x15a/0x164
> [   16.787687]  ? __pfx_kernel_init+0x10/0x10
> [   16.791785]  kernel_init+0x1a/0x130
> [   16.795268]  ret_from_fork+0x29/0x50
> [   16.798840]  </TASK>
> 
> To fix this issue, early initrd must be mapped as encrypted when it is
> being relocated.
> 
> Zelin Deng (2):
>    mm/early_ioremap.c: Always build early_memremap_prot() in x86
>    x86/setup: Preserve _ENC flag when initrd is being relocated
> 
>   arch/x86/Kconfig                    |  1 +
>   arch/x86/kernel/setup.c             | 30 ++++++++++++++++++++++++++++-
>   include/asm-generic/early_ioremap.h |  6 ------
>   mm/early_ioremap.c                  | 21 --------------------
>   4 files changed, 30 insertions(+), 28 deletions(-)
>