From: Ben Hutchings ben@decadent.org.uk
commit b648ab487f31bc4c38941bc770ea97fe394304bb upstream.
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 [bwh: Backported to 5.10/5.15/5.18: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/Kconfig | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2469,7 +2469,7 @@ config RETPOLINE config RETHUNK bool "Enable return-thunks" depends on RETPOLINE && CC_HAS_RETURN_THUNK - 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. @@ -2478,21 +2478,21 @@ 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.