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

Song Liu
2018-08-11T08:04:24Z

On Wed, Aug 8, 2018 at 9:18 PM, Ravi Bangoria
<ravi.bangoria@linux.ibm.com> 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@linux.ibm.com>
> ---
> 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
>