linux-kernel - [PATCH 4.9 36/92] KVM: x86: Make indirect calls in emulator speculation safe

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Message-Id: <20180209133933.771072983@linuxfoundation.org>
Date:   Fri,  9 Feb 2018 14:39:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>, rga@...zon.de,
        Dave Hansen <dave.hansen@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Arjan Van De Ven <arjan.van.de.ven@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: [PATCH 4.9 36/92] KVM: x86: Make indirect calls in emulator speculation safe

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>

(cherry picked from commit 1a29b5b7f347a1a9230c1e0af5b37e3e571588ab)

Replace the indirect calls with CALL_NOSPEC.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Greg KH <gregkh@...uxfoundation.org>
Cc: Jun Nakajima <jun.nakajima@...el.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: rga@...zon.de
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Asit Mallick <asit.k.mallick@...el.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@...el.com>
Cc: Tim Chen <tim.c.chen@...ux.intel.com>
Link: https://lkml.kernel.org/r/20180125095843.595615683@infradead.org
[dwmw2: Use ASM_CALL_CONSTRAINT like upstream, now we have it]
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kvm/emulate.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -25,6 +25,7 @@
 #include <asm/kvm_emulate.h>
 #include <linux/stringify.h>
 #include <asm/debugreg.h>
+#include <asm/nospec-branch.h>
 
 #include "x86.h"
 #include "tss.h"
@@ -1012,8 +1013,8 @@ static __always_inline u8 test_cc(unsign
 	void (*fop)(void) = (void *)em_setcc + 4 * (condition & 0xf);
 
 	flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;
-	asm("push %[flags]; popf; call *%[fastop]"
-	    : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags));
+	asm("push %[flags]; popf; " CALL_NOSPEC
+	    : "=a"(rc) : [thunk_target]"r"(fop), [flags]"r"(flags));
 	return rc;
 }
 
@@ -5306,15 +5307,14 @@ static void fetch_possible_mmx_operand(s
 
 static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))
 {
-	register void *__sp asm(_ASM_SP);
 	ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;
 
 	if (!(ctxt->d & ByteOp))
 		fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
 
-	asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
+	asm("push %[flags]; popf; " CALL_NOSPEC " ; pushf; pop %[flags]\n"
 	    : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
-	      [fastop]"+S"(fop), "+r"(__sp)
+	      [thunk_target]"+S"(fop), ASM_CALL_CONSTRAINT
 	    : "c"(ctxt->src2.val));
 
 	ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);