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SubjectRe: [PATCH 5/5] uprobes: kill insert_vm_struct()->uprobe_mmap()
* Oleg Nesterov <oleg@redhat.com> [2012-07-08 22:30:11]:

> Kill insert_vm_struct()->uprobe_mmap(). It is not needed, nobody
> except arch/ia64/kernel/perfmon.c uses insert_vm_struct(vma) with
> vma->vm_file != NULL.
>

Right, but somebody else might start using this later.
I cant think of a use case though.

> And it is wrong. Again, get_user_pages() can not succeed before
> vma_link(vma) makes is visible to find_vma(). And even if this
> worked, we must not insert the new bp before this mapping is
> visible to vma_prio_tree_foreach() for uprobe_unregister().
>

Agree, we are wrong to do it before vma_link.


> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
> mm/mmap.c | 3 ---
> 1 files changed, 0 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index e5a4614..4fe2697 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2345,9 +2345,6 @@ int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma)
> security_vm_enough_memory_mm(mm, vma_pages(vma)))
> return -ENOMEM;
>
> - if (vma->vm_file && uprobe_mmap(vma))
> - return -EINVAL;
> -
> vma_link(mm, vma, prev, rb_link, rb_parent);
> return 0;
> }

Can we do something like:

vma_link(mm, vma, prev, rb_link, rb_parent);

if (vma->vm_file && uprobe_mmap(vma)) {
/* FIXME: dont know if calling unmap_region is fine here */
unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
return -EINVAL;
}
return 0;

}


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