[PATCH -tip 2/2] [BUGFIX] kprobes: Prohibit probing on func_ptr_is_kernel_text

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Prohibit probing on func_ptr_is_kernel_text().
Since the func_ptr_is_kernel_text() is called from
notifier_call_chain() which is called from int3 handler,
probing it may cause double int3 fault and kernel will
reboot.

This happenes when the kernel built with CONFIG_DEBUG_NOTIFIERS=y.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
---
 kernel/extable.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/extable.c b/kernel/extable.c
index 832cb28..b3b8b6a 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/init.h>
+#include <linux/kprobes.h>
 
 #include <asm/sections.h>
 #include <asm/uaccess.h>
@@ -129,7 +130,7 @@ int kernel_text_address(unsigned long addr)
  * pointer is part of the kernel text, we need to do some
  * special dereferencing first.
  */
-int func_ptr_is_kernel_text(void *ptr)
+int __kprobes func_ptr_is_kernel_text(void *ptr)
 {
 	unsigned long addr;
 	addr = (unsigned long) dereference_function_descriptor(ptr);