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FAILED: patch "[PATCH] x86/speculation: Make all RETbleed mitigations 64-bit only" failed to apply to 5.15-stable tree

PATCH [email protected] 1 participant 1 message Jul 25, 2022

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The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b648ab487f31bc4c38941bc770ea97fe394304bb Mon Sep 17 00:00:00 2001
From: Ben Hutchings <[email protected]>
Date: Sat, 23 Jul 2022 17:22:47 +0200
Subject: [PATCH] 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 f43b9876e857 ("x86/retbleed: Add fine grained Kconfig knobs")
Signed-off-by Ben Hutchings <[email protected]>
Signed-off-by Borislav Petkov <[email protected]>
Cc <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
arch/x86/Kconfig +4 -4
index e58798f636d4..1670a3fed263 100644
@@ -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.