CVE-2024-35803
Assigner: Linux
Published: 2024-05-17T13:23:12.183Z
State: PUBLISHED
descriptions: value: In the Linux kernel, the following vulnerability has been resolved:

x86/efistub: Call mixed mode boot services on the firmware's stack

Normally, the EFI stub calls into the EFI boot services using the stack
that was live when the stub was entered. According to the UEFI spec,
this stack needs to be at least 128k in size - this might seem large but
all asynchronous processing and event handling in EFI runs from the same
stack and so quite a lot of space may be used in practice.

In mixed mode, the situation is a bit different: the bootloader calls
the 32-bit EFI stub entry point, which calls the decompressor's 32-bit
entry point, where the boot stack is set up, using a fixed allocation
of 16k. This stack is still in use when the EFI stub is started in
64-bit mode, and so all calls back into the EFI firmware will be using
the decompressor's limited boot stack.

Due to the placement of the boot stack right after the boot heap, any
stack overruns have gone unnoticed. However, commit

  5c4feadb0011983b ("x86/decompressor: Move global symbol references to C code")

moved the definition of the boot heap into C code, and now the boot
stack is placed right at the base of BSS, where any overruns will
corrupt the end of the .data section.

While it would be possible to work around this by increasing the size of
the boot stack, doing so would affect all x86 systems, and mixed mode
systems are a tiny (and shrinking) fraction of the x86 installed base.

So instead, record the firmware stack pointer value when entering from
the 32-bit firmware, and switch to this stack every time a EFI boot
service call is made.
affected: product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 1da177e4c3f4
lessThan: 2149f8a56e2e
status: affected
versionType: git
version: 1da177e4c3f4
lessThan: 930775060ca3
status: affected
versionType: git
version: 1da177e4c3f4
lessThan: fba7ee718758
status: affected
versionType: git
version: 1da177e4c3f4
lessThan: 725351c03645
status: affected
versionType: git
version: 1da177e4c3f4
lessThan: cefcd4fe2e3a
status: affected
versionType: git
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 6.1.84
lessThanOrEqual: 6.1.*
status: unaffected
versionType: custom
version: 6.6.24
lessThanOrEqual: 6.6.*
status: unaffected
versionType: custom
version: 6.7.12
lessThanOrEqual: 6.7.*
status: unaffected
versionType: custom
version: 6.8.3
lessThanOrEqual: 6.8.*
status: unaffected
versionType: custom
version: 6.9
lessThanOrEqual: *
status: unaffected
versionType: original_commit_for_fix
title: x86/efistub: Call mixed mode boot services on the firmware's stack
x_generator: engine: bippy-d175d3acf727