From: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> commit 3267cb6d3a174ff83d6287dcd5b0047bbd912452 upstream. 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/20230609183632.48706-1-alexander.shishkin@xxxxxxxxxxxxxxx/ [ dhansen: update SPECULATION_MITIGATIONS -> CPU_MITIGATIONS ] Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Reviewed-by: Sohil Mehta <sohil.mehta@xxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc:stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/all/5373262886f2783f054256babdf5a98545dc986b.1706068222.git.pawan.kumar.gupta%40linux.intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/Kconfig | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2217,6 +2217,7 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING config ADDRESS_MASKING bool "Linear Address Masking support" depends on X86_64 + depends on COMPILE_TEST || !CPU_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 Patches currently in stable-queue which might be from pawan.kumar.gupta@xxxxxxxxxxxxxxx are queue-6.6/x86-lam-disable-address_masking-in-most-cases.patch
