linux-kernel - [PATCH -tip 1/2] [BUGFIX] kprobes/x86: Prohibit probing on debug_stack

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Date:	Wed, 30 Oct 2013 10:53:41 +0000
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Fenghua Yu <fenghua.yu@...el.com>,
	Seiji Aguchi <seiji.aguchi@....com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	x86@...nel.org, lkml <linux-kernel@...r.kernel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...e.de>
Subject: [PATCH -tip 1/2] [BUGFIX] kprobes/x86: Prohibit probing on
 debug_stack_*

Prohibit probing on debug_stack_reset and debug_stack_set_zero.
Since the both functions are called from TRACE_IRQS_ON/OFF_DEBUG
macros which run in int3 ist entry, probing it may cause a soft
lockup.

This happens when the kernel built with CONFIG_DYNAMIC_FTRACE=y
and CONFIG_TRACE_IRQFLAGS=y.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Seiji Aguchi <seiji.aguchi@....com>
---
 arch/x86/kernel/cpu/common.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 35e28b0..8712a1a 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -11,6 +11,7 @@
 #include <linux/kgdb.h>
 #include <linux/smp.h>
 #include <linux/io.h>
+#include <linux/kprobes.h>
 
 #include <asm/stackprotector.h>
 #include <asm/perf_event.h>
@@ -1158,7 +1159,7 @@ DEFINE_PER_CPU(struct orig_ist, orig_ist);
 static DEFINE_PER_CPU(unsigned long, debug_stack_addr);
 DEFINE_PER_CPU(int, debug_stack_usage);
 
-int is_debug_stack(unsigned long addr)
+int __kprobes is_debug_stack(unsigned long addr)
 {
 	return __get_cpu_var(debug_stack_usage) ||
 		(addr <= __get_cpu_var(debug_stack_addr) &&
@@ -1167,13 +1168,13 @@ int is_debug_stack(unsigned long addr)
 
 DEFINE_PER_CPU(u32, debug_idt_ctr);
 
-void debug_stack_set_zero(void)
+void __kprobes debug_stack_set_zero(void)
 {
 	this_cpu_inc(debug_idt_ctr);
 	load_current_idt();
 }
 
-void debug_stack_reset(void)
+void __kprobes debug_stack_reset(void)
 {
 	if (WARN_ON(!this_cpu_read(debug_idt_ctr)))
 		return;

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