linux-kernel - [PATCH 1/2] arm: kprobes: Prohibit kprobes on do

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Message-Id: <151945937038.11045.14421944772744094357.stgit@devbox>
Date:   Sat, 24 Feb 2018 17:02:50 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Russell King <linux@...linux.org.uk>
Cc:     Wang Nan <wangnan0@...wei.com>, Will Deacon <will.deacon@....com>,
        Jon Medhurst <tixy@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mhiramat@...nel.org, David Long <dave.long@...aro.org>
Subject: [PATCH 1/2] arm: kprobes: Prohibit kprobes on do_undefinstr

Prohibit kprobes on do_undefinstr because kprobes on
arm is implemented by undefined instruction. This means
if we probe do_undefinstr(), it can cause infinit
recursive exception.

Fixes: 24ba613c9d6c ("ARM kprobes: core code")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 arch/arm/kernel/traps.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 5e3633c24e63..2fe87109ae46 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -19,6 +19,7 @@
 #include <linux/uaccess.h>
 #include <linux/hardirq.h>
 #include <linux/kdebug.h>
+#include <linux/kprobes.h>
 #include <linux/module.h>
 #include <linux/kexec.h>
 #include <linux/bug.h>
@@ -417,7 +418,8 @@ void unregister_undef_hook(struct undef_hook *hook)
 	raw_spin_unlock_irqrestore(&undef_lock, flags);
 }
 
-static int call_undef_hook(struct pt_regs *regs, unsigned int instr)
+static nokprobe_inline
+int call_undef_hook(struct pt_regs *regs, unsigned int instr)
 {
 	struct undef_hook *hook;
 	unsigned long flags;
@@ -490,6 +492,7 @@ asmlinkage void do_undefinstr(struct pt_regs *regs)
 
 	arm_notify_die("Oops - undefined instruction", regs, &info, 0, 6);
 }
+NOKPROBE_SYMBOL(do_undefinstr)
 
 /*
  * Handle FIQ similarly to NMI on x86 systems.