x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized p

x86/efistub: Omit physical KASLR when memory reservations exist

commit 15aa8fb852f995dd234a57f12dfb989044968bb6 upstream.

The legacy decompressor has elaborate logic to ensure that the
randomized physical placement of the decompressed kernel image does not
conflict with any memory reservations, including ones specified on the
command line using mem=, memmap=, efi_fake_mem= or hugepages=, which are
taken into account by the kernel proper at a later stage.

When booting in EFI mode, it is the firmware's job to ensure that the
chosen range does not conflict with any memory reservations that it
knows about, and this is trivially achieved by using the firmware's
memory allocation APIs.

That leaves reservations specified on the command line, though, which
the firmware knows nothing about, as these regions have no other special
significance to the platform. Since commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

these reservations are not taken into account when randomizing the
physical placement, which may result in conflicts where the memory
cannot be reserved by the kernel proper because its own executable image
resides there.

To avoid having to duplicate or reuse the existing complicated logic,
disable physical KASLR entirely when such overrides are specified. These
are mostly diagnostic tools or niche features, and physical KASLR (as
opposed to virtual KASLR, which is much more important as it affects the
memory addresses observed by code executing in the kernel) is something
we can live without.

Closes: https://lkml.kernel.org/r/FA5F6719-8824-4B04-803E-82990E65E627%40akamai.com
Reported-by: Ben Chaney <bchaney@akamai.com>
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Cc: <stable@vger.kernel.org> # v6.1+
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/boot: Move mem_encrypt= parsing to the decompressor

commit cd0d9d92c8bb46e77de62efd7df13069ddd61e7d upstream.

The early SME/SEV code parses the command line very early, in order to
decide wheth

x86/boot: Move mem_encrypt= parsing to the decompressor

commit cd0d9d92c8bb46e77de62efd7df13069ddd61e7d upstream.

The early SME/SEV code parses the command line very early, in order to
decide whether or not memory encryption should be enabled, which needs
to occur even before the initial page tables are created.

This is problematic for a number of reasons:
- this early code runs from the 1:1 mapping provided by the decompressor
or firmware, which uses a different translation than the one assumed by
the linker, and so the code needs to be built in a special way;
- parsing external input while the entire kernel image is still mapped
writable is a bad idea in general, and really does not belong in
security minded code;
- the current code ignores the built-in command line entirely (although
this appears to be the case for the entire decompressor)

Given that the decompressor/EFI stub is an intrinsic part of the x86
bootable kernel image, move the command line parsing there and out of
the core kernel. This removes the need to build lib/cmdline.o in a
special way, or to use RIP-relative LEA instructions in inline asm
blocks.

This involves a new xloadflag in the setup header to indicate
that mem_encrypt=on appeared on the kernel command line.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20240227151907.387873-17-ardb+git@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Remap kernel text read-only before dropping NX attribute

commit 9c55461040a9264b7e44444c53d26480b438eda6 upstream.

Currently, the EFI stub invokes the EFI memory attributes protocol to

x86/efistub: Remap kernel text read-only before dropping NX attribute

commit 9c55461040a9264b7e44444c53d26480b438eda6 upstream.

Currently, the EFI stub invokes the EFI memory attributes protocol to
strip any NX restrictions from the entire loaded kernel, resulting in
all code and data being mapped read-write-execute.

The point of the EFI memory attributes protocol is to remove the need
for all memory allocations to be mapped with both write and execute
permissions by default, and make it the OS loader's responsibility to
transition data mappings to code mappings where appropriate.

Even though the UEFI specification does not appear to leave room for
denying memory attribute changes based on security policy, let's be
cautious and avoid relying on the ability to create read-write-execute
mappings. This is trivially achievable, given that the amount of kernel
code executing via the firmware's 1:1 mapping is rather small and
limited to the .head.text region. So let's drop the NX restrictions only
on that subregion, but not before remapping it as read-only first.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Reinstate soft limit for initrd loading

commit decd347c2a75d32984beb8807d470b763a53b542 upstream.

Commit

8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")

dropped t

x86/efistub: Reinstate soft limit for initrd loading

commit decd347c2a75d32984beb8807d470b763a53b542 upstream.

Commit

8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")

dropped the memcopy of the image's setup header into the boot_params
struct provided to the core kernel, on the basis that EFI boot does not
need it and should rely only on a single protocol to interface with the
boot chain. It is also a prerequisite for being able to increase the
section alignment to 4k, which is needed to enable memory protections
when running in the boot services.

So only the setup_header fields that matter to the core kernel are
populated explicitly, and everything else is ignored. One thing was
overlooked, though: the initrd_addr_max field in the setup_header is not
used by the core kernel, but it is used by the EFI stub itself when it
loads the initrd, where its default value of INT_MAX is used as the soft
limit for memory allocation.

This means that, in the old situation, the initrd was virtually always
loaded in the lower 2G of memory, but now, due to initrd_addr_max being
0x0, the initrd may end up anywhere in memory. This should not be an
issue principle, as most systems can deal with this fine. However, it
does appear to tickle some problems in older UEFI implementations, where
the memory ends up being corrupted, resulting in errors when unpacking
the initramfs.

So set the initrd_addr_max field to INT_MAX like it was before.

Fixes: 8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")
Reported-by: Radek Podgorny <radek@podgorny.cz>
Closes: https://lore.kernel.org/all/a99a831a-8ad5-4cb0-bff9-be637311f771@podgorny.cz
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Reinstate soft limit for initrd loading

commit decd347c2a75d32984beb8807d470b763a53b542 upstream.

Commit

8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")

dropped t

x86/efistub: Reinstate soft limit for initrd loading

commit decd347c2a75d32984beb8807d470b763a53b542 upstream.

Commit

8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")

dropped the memcopy of the image's setup header into the boot_params
struct provided to the core kernel, on the basis that EFI boot does not
need it and should rely only on a single protocol to interface with the
boot chain. It is also a prerequisite for being able to increase the
section alignment to 4k, which is needed to enable memory protections
when running in the boot services.

So only the setup_header fields that matter to the core kernel are
populated explicitly, and everything else is ignored. One thing was
overlooked, though: the initrd_addr_max field in the setup_header is not
used by the core kernel, but it is used by the EFI stub itself when it
loads the initrd, where its default value of INT_MAX is used as the soft
limit for memory allocation.

This means that, in the old situation, the initrd was virtually always
loaded in the lower 2G of memory, but now, due to initrd_addr_max being
0x0, the initrd may end up anywhere in memory. This should not be an
issue principle, as most systems can deal with this fine. However, it
does appear to tickle some problems in older UEFI implementations, where
the memory ends up being corrupted, resulting in errors when unpacking
the initramfs.

So set the initrd_addr_max field to INT_MAX like it was before.

Fixes: 8117961d98fb2 ("x86/efi: Disregard setup header of loaded image")
Reported-by: Radek Podgorny <radek@podgorny.cz>
Closes: https://lore.kernel.org/all/a99a831a-8ad5-4cb0-bff9-be637311f771@podgorny.cz
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Don't clear BSS twice in mixed mode

[ Upstream commit df7ecce842b846a04d087ba85fdb79a90e26a1b0 ]

Clearing BSS should only be done once, at the very beginning.
efi_pe_entry() is the ent

x86/efistub: Don't clear BSS twice in mixed mode

[ Upstream commit df7ecce842b846a04d087ba85fdb79a90e26a1b0 ]

Clearing BSS should only be done once, at the very beginning.
efi_pe_entry() is the entrypoint from the firmware, which may not clear
BSS and so it is done explicitly. However, efi_pe_entry() is also used
as an entrypoint by the mixed mode startup code, in which case BSS will
already have been cleared, and doing it again at this point will corrupt
global variables holding the firmware's GDT/IDT and segment selectors.

So make the memset() conditional on whether the EFI stub is running in
native mode.

Fixes: b3810c5a2cc4a666 ("x86/efistub: Clear decompressor BSS in native EFI entrypoint")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

x86/efistub: Clear decompressor BSS in native EFI entrypoint

[ Upstream commit b3810c5a2cc4a6665f7a65bed5393c75ce3f3aa2 ]

The EFI stub on x86 no longer invokes the decompressor as a subsequent
boot

x86/efistub: Clear decompressor BSS in native EFI entrypoint

[ Upstream commit b3810c5a2cc4a6665f7a65bed5393c75ce3f3aa2 ]

The EFI stub on x86 no longer invokes the decompressor as a subsequent
boot stage, but calls into the decompression code directly while running
in the context of the EFI boot services.

This means that when using the native EFI entrypoint (as opposed to the
EFI handover protocol, which clears BSS explicitly), the firmware PE
image loader is being relied upon to ensure that BSS is zeroed before
the EFI stub is entered from the firmware.

As Radek's report proves, this is a bad idea. Not all loaders do this
correctly, which means some global variables that should be statically
initialized to 0x0 may have junk in them.

So clear BSS explicitly when entering via efi_pe_entry(). Note that
zeroing BSS from C code is not generally safe, but in this case, the
following assignment and dereference of a global pointer variable
ensures that the memset() cannot be deferred or reordered.

Cc: <stable@kernel.org> # v6.1+
Reported-by: Radek Podgorny <radek@podgorny.cz>
Closes: https://lore.kernel.org/all/a99a831a-8ad5-4cb0-bff9-be637311f771@podgorny.cz
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

show more ...

x86/efi: Disregard setup header of loaded image

commit 7e50262229faad0c7b8c54477cd1c883f31cc4a7 upstream.

The native EFI entrypoint does not take a struct boot_params from the
loader, but instead,

x86/efi: Disregard setup header of loaded image

commit 7e50262229faad0c7b8c54477cd1c883f31cc4a7 upstream.

The native EFI entrypoint does not take a struct boot_params from the
loader, but instead, it constructs one from scratch, using the setup
header data placed at the start of the image.

This setup header is placed in a way that permits legacy loaders to
manipulate the contents (i.e., to pass the kernel command line or the
address and size of an initial ramdisk), but EFI boot does not use it in
that way - it only copies the contents that were placed there at build
time, but EFI loaders will not (and should not) manipulate the setup
header to configure the boot. (Commit 63bf28ceb3ebbe76 "efi: x86: Wipe
setup_data on pure EFI boot" deals with some of the fallout of using
setup_data in a way that breaks EFI boot.)

Given that none of the non-zero values that are copied from the setup
header into the EFI stub's struct boot_params are relevant to the boot
now that the EFI stub no longer enters via the legacy decompressor, the
copy can be omitted altogether.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230912090051.4014114-19-ardb@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR

[ Upstream commit 2f77465b05b1270c832b5e2ee27037672ad2a10a ]

The EFI stub's kernel placement logic randomizes the physical placement
o

x86/efistub: Avoid placing the kernel below LOAD_PHYSICAL_ADDR

[ Upstream commit 2f77465b05b1270c832b5e2ee27037672ad2a10a ]

The EFI stub's kernel placement logic randomizes the physical placement
of the kernel by taking all available memory into account, and picking a
region at random, based on a random seed.

When KASLR is disabled, this seed is set to 0x0, and this results in the
lowest available region of memory to be selected for loading the kernel,
even if this is below LOAD_PHYSICAL_ADDR. Some of this memory is
typically reserved for the GFP_DMA region, to accommodate masters that
can only access the first 16 MiB of system memory.

Even if such devices are rare these days, we may still end up with a
warning in the kernel log, as reported by Tom:

swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0

Fix this by tweaking the random allocation logic to accept a low bound
on the placement, and set it to LOAD_PHYSICAL_ADDR.

Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Reported-by: Tom Englund <tomenglund26@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218404
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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x86/efistub: Give up if memory attribute protocol returns an error

[ Upstream commit a7a6a01f88e87dec4bf2365571dd2dc7403d52d0 ]

The recently introduced EFI memory attributes protocol should be used

x86/efistub: Give up if memory attribute protocol returns an error

[ Upstream commit a7a6a01f88e87dec4bf2365571dd2dc7403d52d0 ]

The recently introduced EFI memory attributes protocol should be used
if it exists to ensure that the memory allocation created for the kernel
permits execution. This is needed for compatibility with tightened
requirements related to Windows logo certification for x86 PCs.

Currently, we simply strip the execute protect (XP) attribute from the
entire range, but this might be rejected under some firmware security
policies, and so in a subsequent patch, this will be changed to only
strip XP from the executable region that runs early, and make it
read-only (RO) as well.

In order to catch any issues early, ensure that the memory attribute
protocol works as intended, and give up if it produces spurious errors.

Note that the DXE services based fallback was always based on best
effort, so don't propagate any errors returned by that API.

Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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efi/x86: Avoid physical KASLR on older Dell systems

[ Upstream commit 50d7cdf7a9b1ab6f4f74a69c84e974d5dc0c1bf1 ]

River reports boot hangs with v6.6 and v6.7, and the bisect points to
commit

a1b8

efi/x86: Avoid physical KASLR on older Dell systems

[ Upstream commit 50d7cdf7a9b1ab6f4f74a69c84e974d5dc0c1bf1 ]

River reports boot hangs with v6.6 and v6.7, and the bisect points to
commit

a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")

which moves the memory allocation and kernel decompression from the
legacy decompressor (which executes *after* ExitBootServices()) to the
EFI stub, using boot services for allocating the memory. The memory
allocation succeeds but the subsequent call to decompress_kernel() never
returns, resulting in a failed boot and a hanging system.

As it turns out, this issue only occurs when physical address
randomization (KASLR) is enabled, and given that this is a feature we
can live without (virtual KASLR is much more important), let's disable
the physical part of KASLR when booting on AMI UEFI firmware claiming to
implement revision v2.0 of the specification (which was released in
2006), as this is the version these systems advertise.

Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218173
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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x86/boot: efistub: Assign global boot_params variable

Now that the x86 EFI stub calls into some APIs exposed by the
decompressor (e.g., kaslr_get_random_long()), it is necessary to ensure
that the g

x86/boot: efistub: Assign global boot_params variable

Now that the x86 EFI stub calls into some APIs exposed by the
decompressor (e.g., kaslr_get_random_long()), it is necessary to ensure
that the global boot_params variable is set correctly before doing so.

Note that the decompressor and the kernel proper carry conflicting
declarations for the global variable 'boot_params' so refer to it via an
alias to work around this.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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x86/efistub: Don't try to print after ExitBootService()

setup_e820() is executed after UEFI's ExitBootService has been called.
This causes the firmware to throw an exception because the Console IO
p

x86/efistub: Don't try to print after ExitBootService()

setup_e820() is executed after UEFI's ExitBootService has been called.
This causes the firmware to throw an exception because the Console IO
protocol is supposed to work only during boot service environment. As
per UEFI 2.9, section 12.1:

"This protocol is used to handle input and output of text-based
information intended for the system user during the operation of code
in the boot services environment."

So drop the diagnostic warning from this function. We might add back a
warning that is issued later when initializing the kernel itself.

Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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x86/efistub: Fix PCI ROM preservation in mixed mode

preserve_pci_rom_image() was accessing the romsize field in
efi_pci_io_protocol_t directly instead of using the efi_table_attr()
helper. This prev

x86/efistub: Fix PCI ROM preservation in mixed mode

preserve_pci_rom_image() was accessing the romsize field in
efi_pci_io_protocol_t directly instead of using the efi_table_attr()
helper. This prevents the ROM image from being saved correctly during a
mixed mode boot.

Fixes: 2c3625cb9fa2 ("efi/x86: Fold __setup_efi_pci32() and __setup_efi_pci64() into one function")
Signed-off-by: Mikel Rychliski <mikel@mikelr.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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x86/efistub: Avoid legacy decompressor when doing EFI boot

The bare metal decompressor code was never really intended to run in a
hosted environment such as the EFI boot services, and does a few thi

x86/efistub: Avoid legacy decompressor when doing EFI boot

The bare metal decompressor code was never really intended to run in a
hosted environment such as the EFI boot services, and does a few things
that are becoming problematic in the context of EFI boot now that the
logo requirements are getting tighter: EFI executables will no longer be
allowed to consist of a single executable section that is mapped with
read, write and execute permissions if they are intended for use in a
context where Secure Boot is enabled (and where Microsoft's set of
certificates is used, i.e., every x86 PC built to run Windows).

To avoid stepping on reserved memory before having inspected the E820
tables, and to ensure the correct placement when running a kernel build
that is non-relocatable, the bare metal decompressor moves its own
executable image to the end of the allocation that was reserved for it,
in order to perform the decompression in place. This means the region in
question requires both write and execute permissions, which either need
to be given upfront (which EFI will no longer permit), or need to be
applied on demand using the existing page fault handling framework.

However, the physical placement of the kernel is usually randomized
anyway, and even if it isn't, a dedicated decompression output buffer
can be allocated anywhere in memory using EFI APIs when still running in
the boot services, given that EFI support already implies a relocatable
kernel. This means that decompression in place is never necessary, nor
is moving the compressed image from one end to the other.

Since EFI already maps all of memory 1:1, it is also unnecessary to
create new page tables or handle page faults when decompressing the
kernel. That means there is also no need to replace the special
exception handlers for SEV. Generally, there is little need to do
any of the things that the decompressor does beyond

- initialize SEV encryption, if needed,
- perform the 4/5 level paging switch, if needed,
- decompress the kernel
- relocate the kernel

So do all of this from the EFI stub code, and avoid the bare metal
decompressor altogether.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-24-ardb@kernel.org

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x86/efistub: Perform SNP feature test while running in the firmware

Before refactoring the EFI stub boot flow to avoid the legacy bare metal
decompressor, duplicate the SNP feature check in the EFI

x86/efistub: Perform SNP feature test while running in the firmware

Before refactoring the EFI stub boot flow to avoid the legacy bare metal
decompressor, duplicate the SNP feature check in the EFI stub before
handing over to the kernel proper.

The SNP feature check can be performed while running under the EFI boot
services, which means it can force the boot to fail gracefully and
return an error to the bootloader if the loaded kernel does not
implement support for all the features that the hypervisor enabled.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-23-ardb@kernel.org

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x86/efistub: Prefer EFI memory attributes protocol over DXE services

Currently, the EFI stub relies on DXE services in some cases to clear
non-execute restrictions from page allocations that need to

x86/efistub: Prefer EFI memory attributes protocol over DXE services

Currently, the EFI stub relies on DXE services in some cases to clear
non-execute restrictions from page allocations that need to be
executable. This is dodgy, because DXE services are not specified by
UEFI but by PI, and they are not intended for consumption by OS loaders.
However, no alternative existed at the time.

Now, there is a new UEFI protocol that should be used instead, so if it
exists, prefer it over the DXE services calls.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-18-ardb@kernel.org

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x86/efistub: Perform 4/5 level paging switch from the stub

In preparation for updating the EFI stub boot flow to avoid the bare
metal decompressor code altogether, implement the support code for
swi

x86/efistub: Perform 4/5 level paging switch from the stub

In preparation for updating the EFI stub boot flow to avoid the bare
metal decompressor code altogether, implement the support code for
switching between 4 and 5 levels of paging before jumping to the kernel
proper.

Reuse the newly refactored trampoline that the bare metal decompressor
uses, but relies on EFI APIs to allocate 32-bit addressable memory and
remap it with the appropriate permissions. Given that the bare metal
decompressor will no longer call into the trampoline if the number of
paging levels is already set correctly, it is no longer needed to remove
NX restrictions from the memory range where this trampoline may end up.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20230807162720.545787-17-ardb@kernel.org

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x86/efistub: Clear BSS in EFI handover protocol entrypoint

The so-called EFI handover protocol is value-add from the distros that
permits a loader to simply copy a PE kernel image into memory and ca

x86/efistub: Clear BSS in EFI handover protocol entrypoint

The so-called EFI handover protocol is value-add from the distros that
permits a loader to simply copy a PE kernel image into memory and call
an alternative entrypoint that is described by an embedded boot_params
structure.

Most implementations of this protocol do not bother to check the PE
header for minimum alignment, section placement, etc, and therefore also
don't clear the image's BSS, or even allocate enough memory for it.

Allocating more memory on the fly is rather difficult, but at least
clear the BSS region explicitly when entering in this manner, so that
the EFI stub code does not get confused by global variables that were
not zero-initialized correctly.

When booting in mixed mode, this BSS clearing must occur before any
global state is created, so clear it in the 32-bit asm entry point.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230807162720.545787-7-ardb@kernel.org

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