The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

7d866e38c7e9 ("efi: random: Use 'ACPI reclaim' memory for random seed") 966291f6344d ("efi/libstub: Rename efi_call_early/_runtime macros to be more intuitive") 99ea8b1db2d2 ("efi/libstub: Drop 'table' argument from efi_table_attr() macro") 47c0fd39b7b8 ("efi/libstub: Drop protocol argument from efi_call_proto() macro") cd33a5c1d53e ("efi/libstub: Remove 'sys_table_arg' from all function prototypes") 8173ec7905b5 ("efi/libstub: Drop sys_table_arg from printk routines") c3710de5065d ("efi/libstub/x86: Drop __efi_early() export and efi_config struct") dc29da14ed94 ("efi/libstub: Unify the efi_char16_printk implementations") 2fcdad2a80a6 ("efi/libstub: Get rid of 'sys_table_arg' macro parameter") afc4cc71cf78 ("efi/libstub/x86: Avoid thunking for native firmware calls") 960a8d01834e ("efi/libstub: Use stricter typing for firmware function pointers") e8bd5ddf60ee ("efi/libstub: Drop explicit 32/64-bit protocol definitions") f958efe97596 ("efi/libstub: Distinguish between native/mixed not 32/64 bit") 1786e8301164 ("efi/libstub: Extend native protocol definitions with mixed_mode aliases") 2732ea0d5c0a ("efi/libstub: Use a helper to iterate over a EFI handle array") 58ec655a7573 ("efi/libstub: Remove unused __efi_call_early() macro") 8de8788d2182 ("efi/gop: Unify 32/64-bit functions") 44c84b4ada73 ("efi/gop: Convert GOP structures to typedef and clean up some types") 8d62af177812 ("efi/gop: Remove bogus packed attribute from GOP structures") 4911ee401b7c ("x86/efistub: Disable paging at mixed mode entry")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7d866e38c7e9ece8a096d0d098fa9d92b9d4f97e Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel ardb@kernel.org Date: Thu, 20 Oct 2022 10:39:09 +0200 Subject: [PATCH] efi: random: Use 'ACPI reclaim' memory for random seed

EFI runtime services data is guaranteed to be preserved by the OS, making it a suitable candidate for the EFI random seed table, which may be passed to kexec kernels as well (after refreshing the seed), and so we need to ensure that the memory is preserved without support from the OS itself.

However, runtime services data is intended for allocations that are relevant to the implementations of the runtime services themselves, and so they are unmapped from the kernel linear map, and mapped into the EFI page tables that are active while runtime service invocations are in progress. None of this is needed for the RNG seed.

So let's switch to EFI 'ACPI reclaim' memory: in spite of the name, there is nothing exclusively ACPI about it, it is simply a type of allocation that carries firmware provided data which may or may not be relevant to the OS, and it is left up to the OS to decide whether to reclaim it after having consumed its contents.

Given that in Linux, we never reclaim these allocations, it is a good choice for the EFI RNG seed, as the allocation is guaranteed to survive kexec reboots.

One additional reason for changing this now is to align it with the upcoming recommendation for EFI bootloader provided RNG seeds, which must not use EFI runtime services code/data allocations.

Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: Ard Biesheuvel ardb@kernel.org Reviewed-by: Ilias Apalodimas ilias.apalodimas@linaro.org

diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c index 24aa37535372..33ab56769595 100644 --- a/drivers/firmware/efi/libstub/random.c +++ b/drivers/firmware/efi/libstub/random.c @@ -75,7 +75,12 @@ efi_status_t efi_random_get_seed(void) if (status != EFI_SUCCESS) return status;

- status = efi_bs_call(allocate_pool, EFI_RUNTIME_SERVICES_DATA, + /* + * Use EFI_ACPI_RECLAIM_MEMORY here so that it is guaranteed that the + * allocation will survive a kexec reboot (although we refresh the seed + * beforehand) + */ + status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY, sizeof(*seed) + EFI_RANDOM_SEED_SIZE, (void **)&seed); if (status != EFI_SUCCESS)