linux-kernel - [tip:x86/asm] x86/traps: Fix up general protection faults caused by UMIP

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Date:   Wed, 8 Nov 2017 03:01:40 -0800
From:   tip-bot for Ricardo Neri <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     cmetcalf@...lanox.com, shuah@...nel.org, ravi.v.shankar@...el.com,
        hpa@...or.com, jslaby@...e.cz, pbonzini@...hat.com,
        luto@...nel.org, mingo@...nel.org, tony.luck@...el.com,
        ray.huang@....com, peterz@...radead.org, vbabka@...e.cz,
        paul.gortmaker@...driver.com, mst@...hat.com, dvlasenk@...hat.com,
        mhiramat@...nel.org, corbet@....net, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
        ricardo.neri-calderon@...ux.intel.com, fenghua.yu@...el.com,
        dave.hansen@...ux.intel.com, slaoub@...il.com, tglx@...utronix.de,
        brgerst@...il.com, bp@...en8.de, bp@...e.de, jpoimboe@...hat.com
Subject: [tip:x86/asm] x86/traps: Fix up general protection faults caused by
 UMIP

Commit-ID:  6fc9dc81bff0ea461db534e2672acfdaf76f3e4e
Gitweb:     https://git.kernel.org/tip/6fc9dc81bff0ea461db534e2672acfdaf76f3e4e
Author:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
AuthorDate: Sun, 5 Nov 2017 18:27:55 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 8 Nov 2017 11:16:24 +0100

x86/traps: Fix up general protection faults caused by UMIP

If the User-Mode Instruction Prevention CPU feature is available and
enabled, a general protection fault will be issued if the instructions
sgdt, sldt, sidt, str or smsw are executed from user-mode context
(CPL > 0). If the fault was caused by any of the instructions protected
by UMIP, fixup_umip_exception() will emulate dummy results for these
instructions as follows: in virtual-8086 and protected modes, sgdt, sidt
and smsw are emulated; str and sldt are not emulated. No emulation is done
for user-space long mode processes.

If emulation is successful, the emulated result is passed to the user space
program and no SIGSEGV signal is emitted.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Andy Lutomirski <luto@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Chen Yucong <slaoub@...il.com>
Cc: Chris Metcalf <cmetcalf@...lanox.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Huang Rui <ray.huang@....com>
Cc: Jiri Slaby <jslaby@...e.cz>
Cc: Jonathan Corbet <corbet@....net>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@...el.com>
Cc: Shuah Khan <shuah@...nel.org>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: ricardo.neri@...el.com
Link: http://lkml.kernel.org/r/1509935277-22138-11-git-send-email-ricardo.neri-calderon@linux.intel.com
[ Added curly braces. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/traps.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 42a9c44..ab54bf3 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -60,6 +60,7 @@
 #include <asm/trace/mpx.h>
 #include <asm/mpx.h>
 #include <asm/vm86.h>
+#include <asm/umip.h>
 
 #ifdef CONFIG_X86_64
 #include <asm/x86_init.h>
@@ -513,6 +514,11 @@ do_general_protection(struct pt_regs *regs, long error_code)
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
 	cond_local_irq_enable(regs);
 
+	if (static_cpu_has(X86_FEATURE_UMIP)) {
+		if (user_mode(regs) && fixup_umip_exception(regs))
+			return;
+	}
+
 	if (v8086_mode(regs)) {
 		local_irq_enable();
 		handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);