[PATCH]Fix the order of atomic operations in restore_previous_kprobes

[PATCH]Fix the order of atomic operations in restore_previous_kprobes

[Masami Hiramatsu]

From: Masami Hiramatsu <mhiramat@redhat.com>

Fix the order of atomic operations to prevent overwriting prev_kprobe[0].
To pop values from stack, we must decrement stack index right AFTER
reading values.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
---
Details of this issue was reported to
http://sources.redhat.com/bugzilla/show_bug.cgi?id 71

   arch/ia64/kernel/kprobes.c |    7 ++++---
   1 file changed, 4 insertions(+), 3 deletions(-)

Index: 2.6.24-rc8/arch/ia64/kernel/kprobes.c
=================================--- 2.6.24-rc8.orig/arch/ia64/kernel/kprobes.c	2008-01-17 21:14:01.000000000 -0500
+++ 2.6.24-rc8/arch/ia64/kernel/kprobes.c	2008-01-17 21:14:01.000000000 -0500
@@ -381,9 +381,10 @@
   static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
   {
   	unsigned int i;
-	i = atomic_sub_return(1, &kcb->prev_kprobe_index);
-	__get_cpu_var(current_kprobe) = kcb->prev_kprobe[i].kp;
-	kcb->kprobe_status = kcb->prev_kprobe[i].status;
+	i = atomic_read(&kcb->prev_kprobe_index);
+	__get_cpu_var(current_kprobe) = kcb->prev_kprobe[i-1].kp;
+	kcb->kprobe_status = kcb->prev_kprobe[i-1].status;
+	atomic_sub(1, &kcb->prev_kprobe_index);
   }

   static void __kprobes set_current_kprobe(struct kprobe *p,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com, masami.hiramatsu.pt@hitachi.com

Re: [PATCH]Fix the order of atomic operations in

[Shaohua Li]

On Sat, 2008-01-19 at 00:20 +0800, Masami Hiramatsu wrote:
> From: Masami Hiramatsu <mhiramat@redhat.com>
> 
> Fix the order of atomic operations to prevent overwriting
> prev_kprobe[0].
> To pop values from stack, we must decrement stack index right AFTER
> reading values.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> ---
> Details of this issue was reported to
> http://sources.redhat.com/bugzilla/show_bug.cgi?id 71
> 
>    arch/ia64/kernel/kprobes.c |    7 ++++---
>    1 file changed, 4 insertions(+), 3 deletions(-)
> 
> Index: 2.6.24-rc8/arch/ia64/kernel/kprobes.c
> =================================> --- 2.6.24-rc8.orig/arch/ia64/kernel/kprobes.c  2008-01-17
> 21:14:01.000000000 -0500
> +++ 2.6.24-rc8/arch/ia64/kernel/kprobes.c       2008-01-17
> 21:14:01.000000000 -0500
> @@ -381,9 +381,10 @@
>    static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk
> *kcb)
>    {
>         unsigned int i;
> -       i = atomic_sub_return(1, &kcb->prev_kprobe_index);
> -       __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i].kp;
> -       kcb->kprobe_status = kcb->prev_kprobe[i].status;
> +       i = atomic_read(&kcb->prev_kprobe_index);
> +       __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i-1].kp;
> +       kcb->kprobe_status = kcb->prev_kprobe[i-1].status;
> +       atomic_sub(1, &kcb->prev_kprobe_index);
>    }
> 
>    static void __kprobes set_current_kprobe(struct kprobe *p,
Acked. Thanks for the patch.

Thanks,
Shaohua