Commit b648ab48 authored by Ben Hutchings's avatar Ben Hutchings Committed by Borislav Petkov
Browse files

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: f43b9876 ("x86/retbleed: Add fine grained Kconfig knobs")
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/YtwSR3NNsWp1ohfV@decadent.org.uk
parent efc72a66

arch/x86/Kconfig

+4 −4
Original line number Diff line number Diff line
@@ -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.