The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b648ab487f31bc4c38941bc770ea97fe394304bb Mon Sep 17 00:00:00 2001 From: Ben Hutchings ben@decadent.org.uk Date: Sat, 23 Jul 2022 17:22:47 +0200 Subject: [PATCH] x86/speculation: Make all RETbleed mitigations 64-bit only

The mitigations for RETBleed are currently ineffective on x86_32 since entry_32.S does not use the required macros. However, for an x86_32 target, the kconfig symbols for them are still enabled by default and /sys/devices/system/cpu/vulnerabilities/retbleed will wrongly report that mitigations are in place.

Make all of these symbols depend on X86_64, and only enable RETHUNK by default on X86_64.

Fixes: f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs") Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/YtwSR3NNsWp1ohfV@decadent.org.uk

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index e58798f636d4..1670a3fed263 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2473,7 +2473,7 @@ config RETHUNK bool "Enable return-thunks" depends on RETPOLINE && CC_HAS_RETURN_THUNK select OBJTOOL if HAVE_OBJTOOL - default y + default y if X86_64 help Compile the kernel with the return-thunks compiler option to guard against kernel-to-user data leaks by avoiding return speculation. @@ -2482,21 +2482,21 @@ config RETHUNK

config CPU_UNRET_ENTRY bool "Enable UNRET on kernel entry" - depends on CPU_SUP_AMD && RETHUNK + depends on CPU_SUP_AMD && RETHUNK && X86_64 default y help Compile the kernel with support for the retbleed=unret mitigation.

config CPU_IBPB_ENTRY bool "Enable IBPB on kernel entry" - depends on CPU_SUP_AMD + depends on CPU_SUP_AMD && X86_64 default y help Compile the kernel with support for the retbleed=ibpb mitigation.

config CPU_IBRS_ENTRY bool "Enable IBRS on kernel entry" - depends on CPU_SUP_INTEL + depends on CPU_SUP_INTEL && X86_64 default y help Compile the kernel with support for the spectre_v2=ibrs mitigation.