linux-kernel - Re: [PATCH drivers/misc 0/4] lkdtm: Various clean ups

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Date:   Wed, 24 Jun 2020 23:06:18 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Richard Weinberger <richard.weinberger@...il.com>,
        Richard Weinberger <richard@....at>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        clang-built-linux@...glegroups.com,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH drivers/misc 0/4] lkdtm: Various clean ups

On Wed, Jun 24, 2020 at 06:45:47PM -0700, Randy Dunlap wrote:
> Looks like lkdtm/bugs.c needs to get/use arch/x86/include/asm/processor.h
> but it actually uses arch/x86/um/asm/processor*.h, which does not have the
> needed structs etc.

Should I just test for !UML in bugs.c? (This is all for the
lkdtm_DOUBLE_FAULT() test.) I already do those kinds of checks for the
lkdtm_UNSET_SMEP() test. e.g.:


diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 736675f0a246..f3e7040a7739 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -13,7 +13,7 @@
 #include <linux/uaccess.h>
 #include <linux/slab.h>
 
-#ifdef CONFIG_X86_32
+#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
 #include <asm/desc.h>
 #endif
 
@@ -419,7 +419,7 @@ void lkdtm_UNSET_SMEP(void)
 
 void lkdtm_DOUBLE_FAULT(void)
 {
-#ifdef CONFIG_X86_32
+#if IS_ENABLED(CONFIG_X86_32) && !IS_ENABLED(CONFIG_UML)
 	/*
 	 * Trigger #DF by setting the stack limit to zero.  This clobbers
 	 * a GDT TLS slot, which is okay because the current task will die

-- 
Kees Cook