| 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: x86/speculation: Make all RETbleed mitigations 64-bit only |
| |
| 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 |
| @@ -2447,7 +2447,7 @@ 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. |
| @@ -2456,21 +2456,21 @@ 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. |
