linux-stable.git/drivers/firmware/efi, branch linux-6.0.y

efi: random: combine bootloader provided RNG seed with RNG protocol output

2023-01-12T11:00:48+00:00

commit 196dff2712ca5a2e651977bb2fe6b05474111a83 upstream.

Instead of blindly creating the EFI random seed configuration table if
the RNG protocol is implemented and works, check whether such a EFI
configuration table was provided by an earlier boot stage and if so,
concatenate the existing and the new seeds, leaving it up to the core
code to mix it in and credit it the way it sees fit.

This can be used for, e.g., systemd-boot, to pass an additional seed to
Linux in a way that can be consumed by the kernel very early. In that
case, the following definitions should be used to pass the seed to the
EFI stub:

struct linux_efi_random_seed {
      u32     size; // of the 'seed' array in bytes
      u8      seed[];
};

The memory for the struct must be allocated as EFI_ACPI_RECLAIM_MEMORY
pool memory, and the address of the struct in memory should be installed
as a EFI configuration table using the following GUID:

LINUX_EFI_RANDOM_SEED_TABLE_GUID        1ce1e5bc-7ceb-42f2-81e5-8aadf180f57b

Note that doing so is safe even on kernels that were built without this
patch applied, but the seed will simply be overwritten with a seed
derived from the EFI RNG protocol, if available. The recommended seed
size is 32 bytes, and seeds larger than 512 bytes are considered
corrupted and ignored entirely.

In order to preserve forward secrecy, seeds from previous bootloaders
are memzero'd out, and in order to preserve memory, those older seeds
are also freed from memory. Freeing from memory without first memzeroing
is not safe to do, as it's possible that nothing else will ever
overwrite those pages used by EFI.

Reviewed-by: Jason A. Donenfeld 
[ardb: incorporate Jason's followup changes to extend the maximum seed
       size on the consumer end, memzero() it and drop a needless printk]
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Jason A. Donenfeld 
Signed-off-by: Greg Kroah-Hartman

efi: efivars: Fix variable writes with unsupported query_variable_store()

2022-11-10T17:17:34+00:00

commit f11a74b45d330ad1ab986852b099747161052526 upstream.

Commit 8a254d90a775 ("efi: efivars: Fix variable writes without
query_variable_store()") addressed an issue that was introduced during
the EFI variable store refactor, where alternative implementations of
the efivars layer that lacked query_variable_store() would no longer
work.

Unfortunately, there is another case to consider here, which was missed:
if the efivars layer is backed by the EFI runtime services as usual, but
the EFI implementation predates the introduction of QueryVariableInfo(),
we will return EFI_UNSUPPORTED, and this is no longer being dealt with
correctly.

So let's fix this, and while at it, clean up the code a bit, by merging
the check_var_size() routines as well as their callers.

Cc:  # v6.0
Fixes: bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer")
Signed-off-by: Ard Biesheuvel 
Tested-by: Aditya Garg 
Signed-off-by: Greg Kroah-Hartman

efi: random: Use 'ACPI reclaim' memory for random seed

2022-11-10T17:17:34+00:00

commit 7d866e38c7e9ece8a096d0d098fa9d92b9d4f97e upstream.

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:  # v4.14+
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Ilias Apalodimas 
Signed-off-by: Greg Kroah-Hartman

efi: random: reduce seed size to 32 bytes

2022-11-10T17:17:34+00:00

commit 161a438d730dade2ba2b1bf8785f0759aba4ca5f upstream.

We no longer need at least 64 bytes of random seed to permit the early
crng init to complete. The RNG is now based on Blake2s, so reduce the
EFI seed size to the Blake2s hash size, which is sufficient for our
purposes.

While at it, drop the READ_ONCE(), which was supposed to prevent size
from being evaluated after seed was unmapped. However, this cannot
actually happen, so READ_ONCE() is unnecessary here.

Cc:  # v4.14+
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Jason A. Donenfeld 
Acked-by: Ilias Apalodimas 
Signed-off-by: Greg Kroah-Hartman

efi/tpm: Pass correct address to memblock_reserve

2022-11-10T17:17:26+00:00

[ Upstream commit f4cd18c5b2000df0c382f6530eeca9141ea41faf ]

memblock_reserve() expects a physical address, but the address being
passed for the TPM final events log is what was returned from
early_memremap(). This results in something like the following:

[    0.000000] memblock_reserve: [0xffffffffff2c0000-0xffffffffff2c00e4] efi_tpm_eventlog_init+0x324/0x370

Pass the address from efi like what is done for the TPM events log.

Fixes: c46f3405692d ("tpm: Reserve the TPM final events table")
Cc: Matthew Garrett 
Cc: Jarkko Sakkinen 
Cc: Bartosz Szczepanek 
Cc: Ard Biesheuvel 
Signed-off-by: Jerry Snitselaar 
Acked-by: Jarkko Sakkinen 
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Sasha Levin

efi: ssdt: Don't free memory if ACPI table was loaded successfully

2022-10-26T10:22:57+00:00

commit 4b017e59f01097f19b938f6dc4dc2c4720701610 upstream.

Amadeusz reports KASAN use-after-free errors introduced by commit
3881ee0b1edc ("efi: avoid efivars layer when loading SSDTs from
variables"). The problem appears to be that the memory that holds the
new ACPI table is now freed unconditionally, instead of only when the
ACPI core reported a failure to load the table.

So let's fix this, by omitting the kfree() on success.

Cc:  # v6.0
Link: https://lore.kernel.org/all/a101a10a-4fbb-5fae-2e3c-76cf96ed8fbd@linux.intel.com/
Fixes: 3881ee0b1edc ("efi: avoid efivars layer when loading SSDTs from variables")
Reported-by: Amadeusz Sławiński 
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Greg Kroah-Hartman

efi: efivars: Fix variable writes without query_variable_store()

2022-10-26T10:22:57+00:00

commit 8a254d90a77580244ec57e82bca7eb65656cc167 upstream.

Commit bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer")
refactored the efivars layer so that the 'business logic' related to
which UEFI variables affect the boot flow in which way could be moved
out of it, and into the efivarfs driver.

This inadvertently broke setting variables on firmware implementations
that lack the QueryVariableInfo() boot service, because we no longer
tolerate a EFI_UNSUPPORTED result from check_var_size() when calling
efivar_entry_set_get_size(), which now ends up calling check_var_size()
a second time inadvertently.

If QueryVariableInfo() is missing, we support writes of up to 64k -
let's move that logic into check_var_size(), and drop the redundant
call.

Cc:  # v6.0
Fixes: bbc6d2c6ef22 ("efi: vars: Switch to new wrapper layer")
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Greg Kroah-Hartman

efi: libstub: drop pointless get_memory_map() call

2022-10-21T10:37:54+00:00

commit d80ca810f096ff66f451e7a3ed2f0cd9ef1ff519 upstream.

Currently, the non-x86 stub code calls get_memory_map() redundantly,
given that the data it returns is never used anywhere. So drop the call.

Cc:  # v4.14+
Fixes: 24d7c494ce46 ("efi/arm-stub: Round up FDT allocation to mapping size")
Signed-off-by: Ard Biesheuvel 
Signed-off-by: Greg Kroah-Hartman

efi: libstub: check Shim mode using MokSBStateRT

2022-09-22T08:15:44+00:00

We currently check the MokSBState variable to decide whether we should
treat UEFI secure boot as being disabled, even if the firmware thinks
otherwise. This is used by shim to indicate that it is not checking
signatures on boot images. In the kernel, we use this to relax lockdown
policies.

However, in cases where shim is not even being used, we don't want this
variable to interfere with lockdown, given that the variable may be
non-volatile and therefore persist across a reboot. This means setting
it once will persistently disable lockdown checks on a given system.

So switch to the mirrored version of this variable, called MokSBStateRT,
which is supposed to be volatile, and this is something we can check.

Cc:  # v4.19+
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Ilias Apalodimas 
Reviewed-by: Peter Jones

efi: x86: Wipe setup_data on pure EFI boot

2022-09-22T08:12:51+00:00

When booting the x86 kernel via EFI using the LoadImage/StartImage boot
services [as opposed to the deprecated EFI handover protocol], the setup
header is taken from the image directly, and given that EFI's LoadImage
has no Linux/x86 specific knowledge regarding struct bootparams or
struct setup_header, any absolute addresses in the setup header must
originate from the file and not from a prior loading stage.

Since we cannot generally predict where LoadImage() decides to load an
image (*), such absolute addresses must be treated as suspect: even if a
prior boot stage intended to make them point somewhere inside the
[signed] image, there is no way to validate that, and if they point at
an arbitrary location in memory, the setup_data nodes will not be
covered by any signatures or TPM measurements either, and could be made
to contain an arbitrary sequence of SETUP_xxx nodes, which could
interfere quite badly with the early x86 boot sequence.

(*) Note that, while LoadImage() does take a buffer/size tuple in
addition to a device path, which can be used to provide the image
contents directly, it will re-allocate such images, as the memory
footprint of an image is generally larger than the PE/COFF file
representation.

Cc:  # v5.10+
Link: https://lore.kernel.org/all/20220904165321.1140894-1-Jason@zx2c4.com/
Signed-off-by: Ard Biesheuvel 
Acked-by: Jason A. Donenfeld