Re: [PATCH v8 4/6] Uprobes/sdt: Prevent multiple reference counter for same uprobe

[Song Liu]

On Wed, Aug 8, 2018 at 9:18 PM, Ravi Bangoria
<ravi.bangoria@xxxxxxxxxxxxx> wrote:
> We assume to have only one reference counter for one uprobe.
> Don't allow user to register multiple uprobes having same
> inode+offset but different reference counter.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> ---
>  kernel/events/uprobes.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 61b0481ef417..492a0e005b4d 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -689,6 +689,12 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
>         cur_uprobe = insert_uprobe(uprobe);
>         /* a uprobe exists for this inode:offset combination */
>         if (cur_uprobe) {
> +               if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
> +                       pr_warn("Reference counter offset mismatch.\n");
We should print more information here, including the inode, the offset
and both ref_ctr_offset.

> +                       put_uprobe(cur_uprobe);
> +                       kfree(uprobe);
> +                       return ERR_PTR(-EINVAL);
> +               }
>                 kfree(uprobe);
>                 uprobe = cur_uprobe;
>         }
> @@ -1103,6 +1109,9 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
>         uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
>         if (!uprobe)
>                 return -ENOMEM;
> +       if (IS_ERR(uprobe))
> +               return PTR_ERR(uprobe);
> +
>         /*
>          * We can race with uprobe_unregister()->delete_uprobe().
>          * Check uprobe_is_active() and retry if it is false.
> --
> 2.14.4
>