linux-kernel - [tip:x86/urgent] x86/espfix/64: Fix espfix double-fault handling on 5-level systems

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Message-ID: <tip-c739f930be1dd5fd949030e3475a884fe06dae9b@git.kernel.org>
Date:   Fri, 15 Dec 2017 10:34:12 -0800
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        David.Laight@...lab.com, tglx@...utronix.de, mingo@...nel.org,
        kirill@...temov.name, bp@...en8.de,
        kirill.shutemov@...ux.intel.com, dave.hansen@...el.com,
        keescook@...omium.org, hpa@...or.com, luto@...nel.org,
        peterz@...radead.org, brgerst@...il.com
Subject: [tip:x86/urgent] x86/espfix/64: Fix espfix double-fault handling on
 5-level systems

Commit-ID:  c739f930be1dd5fd949030e3475a884fe06dae9b
Gitweb:     https://git.kernel.org/tip/c739f930be1dd5fd949030e3475a884fe06dae9b
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Tue, 12 Dec 2017 07:56:36 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 15 Dec 2017 16:58:53 +0100

x86/espfix/64: Fix espfix double-fault handling on 5-level systems

Using PGDIR_SHIFT to identify espfix64 addresses on 5-level systems
was wrong, and it resulted in panics due to unhandled double faults.
Use P4D_SHIFT instead, which is correct on 4-level and 5-level
machines.

This fixes a panic when running x86 selftests on 5-level machines.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: David Laight <David.Laight@...lab.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Kirill A. Shutemov <kirill@...temov.name>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Fixes: 1d33b219563f ("x86/espfix: Add support for 5-level paging")
Link: http://lkml.kernel.org/r/24c898b4f44fdf8c22d93703850fb384ef87cfdc.1513035461.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index b7b0f74..c751518 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -355,7 +355,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
 	 *
 	 * No need for ist_enter here because we don't use RCU.
 	 */
-	if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
+	if (((long)regs->sp >> P4D_SHIFT) == ESPFIX_PGD_ENTRY &&
 		regs->cs == __KERNEL_CS &&
 		regs->ip == (unsigned long)native_irq_return_iret)
 	{