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x86/speculation: Make all RETbleed mitigations 64-bit only

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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: f43b9876e8 ("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
This commit is contained in:
Ben Hutchings 2022-07-23 17:22:47 +02:00 committed by Borislav Petkov
parent efc72a665a
commit b648ab487f
1 changed files with 4 additions and 4 deletions
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8
arch/x86/Kconfig
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@ -2473,7 +2473,7 @@ config RETHUNK
bool "Enable return-thunks" bool "Enable return-thunks"
depends on RETPOLINE && CC_HAS_RETURN_THUNK depends on RETPOLINE && CC_HAS_RETURN_THUNK
select OBJTOOL if HAVE_OBJTOOL select OBJTOOL if HAVE_OBJTOOL
default y default y if X86_64
help help
Compile the kernel with the return-thunks compiler option to guard Compile the kernel with the return-thunks compiler option to guard
against kernel-to-user data leaks by avoiding return speculation. against kernel-to-user data leaks by avoiding return speculation.
@ -2482,21 +2482,21 @@ config RETHUNK
config CPU_UNRET_ENTRY config CPU_UNRET_ENTRY
bool "Enable UNRET on kernel entry" bool "Enable UNRET on kernel entry"
depends on CPU_SUP_AMD && RETHUNK depends on CPU_SUP_AMD && RETHUNK && X86_64
default y default y
help help
Compile the kernel with support for the retbleed=unret mitigation. Compile the kernel with support for the retbleed=unret mitigation.
config CPU_IBPB_ENTRY config CPU_IBPB_ENTRY
bool "Enable IBPB on kernel entry" bool "Enable IBPB on kernel entry"
depends on CPU_SUP_AMD depends on CPU_SUP_AMD && X86_64
default y default y
help help
Compile the kernel with support for the retbleed=ibpb mitigation. Compile the kernel with support for the retbleed=ibpb mitigation.
config CPU_IBRS_ENTRY config CPU_IBRS_ENTRY
bool "Enable IBRS on kernel entry" bool "Enable IBRS on kernel entry"
depends on CPU_SUP_INTEL depends on CPU_SUP_INTEL && X86_64
default y default y
help help
Compile the kernel with support for the spectre_v2=ibrs mitigation. Compile the kernel with support for the spectre_v2=ibrs mitigation.