2008-01-18 16:21:36

by Masami Hiramatsu

Subject: [PATCH]Fix the order of atomic operations in restore_previous_kprobes on ia64

From: Masami Hiramatsu <[email protected]>

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 <[email protected]>
---
Details of this issue was reported to
http://sources.redhat.com/bugzilla/show_bug.cgi?id=2071

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: [email protected], [email protected]

2008-01-22 01:07:51

by Shaohua Li

Subject: Re: [PATCH]Fix the order of atomic operations in restore_previous_kprobes on ia64

On Sat, 2008-01-19 at 00:20 +0800, Masami Hiramatsu wrote:
> From: Masami Hiramatsu <[email protected]>
>
> 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 <[email protected]>
> ---
> Details of this issue was reported to
> http://sources.redhat.com/bugzilla/show_bug.cgi?id=2071
>
> 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