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>

4 files changed, 5 insertions, 9 deletions

diff --git a/arch/x86/kernel/kprobes_32.c b/arch/x86/kernel/kprobes_32.c
index d87a523070d1..3a020f79f82b 100644
--- a/arch/x86/kernel/kprobes_32.c
+++ b/arch/x86/kernel/kprobes_32.c
@@ -727,9 +727,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 
         if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
                 if (&regs->esp != kcb->jprobe_saved_esp) {
-                        struct pt_regs *saved_regs =
-                            container_of(kcb->jprobe_saved_esp,
-                                            struct pt_regs, esp);
+                        struct pt_regs *saved_regs = &kcb->jprobe_saved_regs;
                         printk("current esp %p does not match saved esp %p\n",
                                &regs->esp, kcb->jprobe_saved_esp);
                         printk("Saved registers for jprobe %p\n", jp);
diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index 0c467644589c..a575059fb420 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);
diff --git a/include/asm-x86/kprobes_32.h b/include/asm-x86/kprobes_32.h
index b772d5b38685..9fe8f3bddfd5 100644
--- a/include/asm-x86/kprobes_32.h
+++ b/include/asm-x86/kprobes_32.h
@@ -73,7 +73,7 @@ struct kprobe_ctlblk {
         unsigned long kprobe_status;
         unsigned long kprobe_old_eflags;
         unsigned long kprobe_saved_eflags;
-        long *jprobe_saved_esp;
+        unsigned long *jprobe_saved_esp;
         struct pt_regs jprobe_saved_regs;
         kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
         struct prev_kprobe prev_kprobe;
diff --git a/include/asm-x86/kprobes_64.h b/include/asm-x86/kprobes_64.h
index 53f4d8507354..743d76218fc9 100644
--- a/include/asm-x86/kprobes_64.h
+++ b/include/asm-x86/kprobes_64.h
@@ -66,7 +66,7 @@ struct kprobe_ctlblk {
         unsigned long kprobe_status;
         unsigned long kprobe_old_rflags;
         unsigned long kprobe_saved_rflags;
-        long *jprobe_saved_rsp;
+        unsigned long *jprobe_saved_rsp;
         struct pt_regs jprobe_saved_regs;
         kprobe_opcode_t jprobes_stack[MAX_STACK_SIZE];
         struct prev_kprobe prev_kprobe;