x86: jprobe bugfix

jprobe for x86-64 may cause kernel page fault when the jprobe_return()
is called from incorrect function.

- Use jprobe_saved_regs instead getting it from stack.
  (Especially on x86-64, it may get incorrect data, because
   pt_regs can not be get by using container_of(rsp))
- Change the type of stack pointer to unsigned long *.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 4 deletions

diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index 0c467644589..a575059fb42 100644
--- a/arch/x86/kernel/kprobes_64.c
+++ b/arch/x86/kernel/kprobes_64.c
@@ -716,10 +716,8 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
         struct jprobe *jp = container_of(p, struct jprobe, kp);
 
         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
-                if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
-                        struct pt_regs *saved_regs =
-                            container_of(kcb->jprobe_saved_rsp,
-                                            struct pt_regs, rsp);
+                if ((unsigned long *)regs->rsp != kcb->jprobe_saved_rsp) {
+                        struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
                         printk("current rsp %p does not match saved rsp %p\n",
                                (long *)regs->rsp, kcb->jprobe_saved_rsp);
                         printk("Saved registers for jprobe %p\n", jp);