This reverts commit 3267cb6d3a174ff83d6287dcd5b0047bbd912452. LASS mitigates the Spectre based on LAM (SLAM) [1] and the previous commit made LAM depend on LASS, so we no longer need to disable LAM at compile time, so revert the commit that disables LAM. Adjust USER_PTR_MAX if LAM enabled, allowing tag bits to be set for userspace pointers. The value for the constant is defined in a way to avoid overflow compiler warning on 32-bit config. [1] https://download.vusec.net/papers/slam_sp24.pdf Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> --- arch/x86/Kconfig | 1 - arch/x86/kernel/cpu/common.c | 5 +---- 2 files changed, 1 insertion(+), 5 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 71019b3b54ea..2b48e916b754 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2181,7 +2181,6 @@ 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 diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 97a228f917a9..6f2ae9e702bc 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2558,11 +2558,8 @@ void __init arch_cpu_finalize_init(void) if (IS_ENABLED(CONFIG_X86_64)) { unsigned long USER_PTR_MAX = TASK_SIZE_MAX; - /* - * Enable this when LAM is gated on LASS support if (cpu_feature_enabled(X86_FEATURE_LAM)) - USER_PTR_MAX = (1ul << 63) - PAGE_SIZE; - */ + USER_PTR_MAX = (-1UL >> 1) & PAGE_MASK; runtime_const_init(ptr, USER_PTR_MAX); /* -- 2.47.2
