Intel feature Linear Address Masking (LAM) has a weakness related to
transient execution as described in the SLAM paper[1]. Unless Linear
Address Space Separation (LASS) is enabled this weakness may be
exploitable.
Until kernel adds support for LASS[2], only allow LAM for COMPILE_TEST,
or when speculation mitigations have been disabled at compile time,
otherwise keep LAM disabled.
There are no processors in market that support LAM yet, so currently
nobody is affected by this issue.
[1] SLAM: https://download.vusec.net/papers/slam_sp24.pdf
[2] LASS: https://lore.kernel.org/lkml/[email protected]/
Cc: [email protected] # v6.4+
Acked-by: Kirill A. Shutemov <[email protected]>
Reviewed-by: Sohil Mehta <[email protected]>
Signed-off-by: Pawan Gupta <[email protected]>
---
v2:
- Updated commit message to reflect that currently there is no exposure
of this issue.
- Added review tags.
arch/x86/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1566748f16c4..794517df8068 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2270,6 +2270,7 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING
config ADDRESS_MASKING
bool "Linear Address Masking support"
depends on X86_64
+ depends on COMPILE_TEST || !SPECULATION_MITIGATIONS # wait for LASS
help
Linear Address Masking (LAM) modifies the checking that is applied
to 64-bit linear addresses, allowing software to use of the
base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a
--
2.34.1