Messages in this thread | | | Date | Fri, 13 Jul 2012 15:29:16 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 5/5] uprobes: kill insert_vm_struct()->uprobe_mmap() |
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On 07/13, Srikar Dronamraju wrote: > > * 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.
Unlikely, I think...
> I cant think of a use case though.
Yes.
> > 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; > }
Yes, I was thinking about the possible fix, but afaics this is not enough. At least this needs vm_unacct_memory(). And I am not sure about unmap_region...
The main problem is that I have no idea how could I test the fix. Once again, currently this file can't be probed.
So. Can't we kill this obviously wrong and unneeded (at least currently) code? Currently uprobe_mmap/munmap logic is not correct (I'll try to send more fixes after I return from vacation), it would be nice to remove the callsite.
If somebody else will use insert_vm_struct() to mmap the can-be-uprobed file then yes, we will need to add uprobe_mmap() somewhere. But until then, the right fix is not clear and not testable.
Oleg.
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