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From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Ingo Molnar <mingo@redhat.com>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>, peterz@infradead.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andrea Righi <righi.andrea@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH v2 3/9] x86/kprobes: Prohibit probing on functions before kprobe_int3_handler()
Date:   Sat, 12 Jan 2019 11:27:05 +0900
Message-Id: <154726002552.18060.16235456056729209714.stgit@devbox>
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Prohibit probing on the functions called before kprobe_int3_handler()
in do_int3(). More specifically, ftrace_int3_handler(),
poke_int3_handler(), and ist_enter(). And since rcu_nmi_enter() is
called by ist_enter(), it also should be marked as NOKPROBE_SYMBOL.

Since those are handled before kprobe_int3_handler(), probing those
functions can cause a breakpoint recursion and crash the kernel.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/kernel/alternative.c |    3 ++-
 arch/x86/kernel/ftrace.c      |    3 ++-
 arch/x86/kernel/traps.c       |    1 +
 kernel/rcu/tree.c             |    2 ++
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index ebeac487a20c..e8b628b1b279 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -11,6 +11,7 @@
 #include <linux/stop_machine.h>
 #include <linux/slab.h>
 #include <linux/kdebug.h>
+#include <linux/kprobes.h>
 #include <asm/text-patching.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
@@ -764,8 +765,8 @@ int poke_int3_handler(struct pt_regs *regs)
 	regs->ip = (unsigned long) bp_int3_handler;
 
 	return 1;
-
 }
+NOKPROBE_SYMBOL(poke_int3_handler);
 
 /**
  * text_poke_bp() -- update instructions on live kernel on SMP
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 7ee8067cbf45..22a548919228 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -269,7 +269,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	return ret;
 }
 
-static int is_ftrace_caller(unsigned long ip)
+static nokprobe_inline int is_ftrace_caller(unsigned long ip)
 {
 	if (ip == ftrace_update_func)
 		return 1;
@@ -299,6 +299,7 @@ int ftrace_int3_handler(struct pt_regs *regs)
 
 	return 1;
 }
+NOKPROBE_SYMBOL(ftrace_int3_handler);
 
 static int ftrace_write(unsigned long ip, const char *val, int size)
 {
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a7..e289ce1332ab 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -111,6 +111,7 @@ void ist_enter(struct pt_regs *regs)
 	/* This code is a bit fragile.  Test it. */
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work");
 }
+NOKPROBE_SYMBOL(ist_enter);
 
 void ist_exit(struct pt_regs *regs)
 {
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9180158756d2..74db52a0a466 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -62,6 +62,7 @@
 #include <linux/suspend.h>
 #include <linux/ftrace.h>
 #include <linux/tick.h>
+#include <linux/kprobes.h>
 
 #include "tree.h"
 #include "rcu.h"
@@ -872,6 +873,7 @@ void rcu_nmi_enter(void)
 {
 	rcu_nmi_enter_common(false);
 }
+NOKPROBE_SYMBOL(rcu_nmi_enter);
 
 /**
  * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle