On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
>
> Use vma_next() and remove reference to the start of the linked list
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> kernel/bpf/task_iter.c | 21 ++++-----------------
> 1 file changed, 4 insertions(+), 17 deletions(-)
>
> diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> index b48750bfba5a..2d964743f1e6 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -299,8 +299,8 @@ struct bpf_iter_seq_task_vma_info {
> };
>
> enum bpf_task_vma_iter_find_op {
> - task_vma_iter_first_vma, /* use mm->mmap */
> - task_vma_iter_next_vma, /* use curr_vma->vm_next */
> + task_vma_iter_first_vma, /* use find_vma() with addr 0 */
> + task_vma_iter_next_vma, /* use vma_next() with curr_vma */
> task_vma_iter_find_vma, /* use find_vma() to find next vma */
> };
>
> @@ -400,24 +400,11 @@ task_vma_seq_get_next(struct bpf_iter_seq_task_vma_info *info)
>
> switch (op) {
> case task_vma_iter_first_vma:
> - curr_vma = curr_task->mm->mmap;
> + curr_vma = find_vma(curr_task->mm, 0);
> break;
> case task_vma_iter_next_vma:
> - curr_vma = curr_vma->vm_next;
> - break;
> case task_vma_iter_find_vma:
> - /* We dropped mmap_lock so it is necessary to use find_vma
> - * to find the next vma. This is similar to the mechanism
> - * in show_smaps_rollup().
> - */
> - curr_vma = find_vma(curr_task->mm, info->prev_vm_end - 1);
> - /* case 1) and 4.2) above just use curr_vma */
> -
> - /* check for case 2) or case 4.1) above */
> - if (curr_vma &&
> - curr_vma->vm_start == info->prev_vm_start &&
> - curr_vma->vm_end == info->prev_vm_end)
> - curr_vma = curr_vma->vm_next;
> + curr_vma = find_vma(curr_task->mm, curr_vma->vm_end);
Are you sure curr_vma is valid here and we can read its vm_end? Because I
have no idea, but lots of doubts.
> break;
> }
> if (!curr_vma) {
