Re: [PATCH 1/1] x86/power: only verify usable RAM regions during hibernation E820 check

[Rafael J. Wysocki]

On Sat, Jun 20, 2026 at 10:16 AM Marco Scardovi <scardracs@xxxxxxxxxxx> wrote:
>
> On some UEFI platforms (such as the HP OmniBook X Flip), resuming from
> hibernation fails with 'Hibernate inconsistent memory map detected!'
> even though the usable system RAM configuration is identical.

That may not be sufficient for the image kernel to work after resuming though.

> This happens because the UEFI firmware or bootloader (like GRUB) makes
> non-deterministic allocations or shifts reserved/ACPI memory regions
> dynamically across boots,

The boot loader has nothing to do with this, the memory map comes from
the UEFI firmware.

> which changes the CRC32 checksum computed
> over the entire E820 table (which includes non-RAM types like reserved,
> ACPI, NVS, and unusable memory).
>
> Fix this by modifying compute_e820_crc32() to only calculate the
> checksum over memory map entries of type E820_TYPE_RAM. Usable system
> RAM layout is still verified to ensure data safety, but dynamic shifts
> in ACPI and other reserved ranges are ignored.

Which is risky because the image kernel may access stuff located in
those non-RAM memory regions (for instance, ACPI tables, AML operation
regions, UEFI runtime variables, etc.).

Hibernation in Linux simply cannot cope with a changing memory map in
general, sorry about that.

> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221569
> Fixes: f5d1499ae209 ("PM: hibernate: x86: Use crc32 instead of md5 for hibernation e820 integrity check")
> Assisted-by: Antigravity:gemini-3.5-flash
> Signed-off-by: Marco Scardovi <scardracs@xxxxxxxxxxx>
> ---
>  arch/x86/power/hibernate.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/power/hibernate.c b/arch/x86/power/hibernate.c
> index a2294c1649f6..752a490bc3d2 100644
> --- a/arch/x86/power/hibernate.c
> +++ b/arch/x86/power/hibernate.c
> @@ -70,12 +70,19 @@ struct restore_data_record {
>   *
>   * Return: the resulting checksum
>   */
> -static inline u32 compute_e820_crc32(struct e820_table *table)
> +static u32 compute_e820_crc32(struct e820_table *table)
>  {
> -       int size = offsetof(struct e820_table, entries) +
> -               sizeof(struct e820_entry) * table->nr_entries;
> +       u32 crc = ~0;
> +       int i;
> +
> +       for (i = 0; i < table->nr_entries; i++) {
> +               if (table->entries[i].type == E820_TYPE_RAM) {
> +                       crc = crc32_le(crc, (unsigned char const *)&table->entries[i],
> +                                      sizeof(struct e820_entry));
> +               }
> +       }
>
> -       return ~crc32_le(~0, (unsigned char const *)table, size);
> +       return ~crc;
>  }
>
>  #ifdef CONFIG_X86_64
> --
> 2.54.0
>
>