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

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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>
This commit is contained in:
Ben Hutchings 2022-07-23 17:22:47 +02:00 committed by Greg Kroah-Hartman
parent 4fd9cb57a3
commit 45b69848a2
1 changed files with 4 additions and 4 deletions
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8
arch/x86/Kconfig
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@ -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.