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

From: Masami Hiramatsu
Date: Wed Oct 30 2013 - 06:53:56 EST

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

This happenes when the kernel built with CONFIG_DEBUG_NOTIFIERS=y.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: "Uwe Kleine-KÃnig" <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
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);

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