On Thu, May 01, 2008 at 10:43:25PM +0300, Adrian Bunk wrote:
> > > - struct vm_area_struct *vma, *prev;
> > > + struct vm_area_struct *vma, *prev = NULL;
> >
> > gcc bug -- it's failing to notice that find_vma_prepare() will always
> > initialise pprev.
> >...
>
> You miss the "return" inside the while() loop in find_vma_prepare().
>
> I do not know whether the code is correct, but the answer is not that
> easy.
You're right, it isn't that easy.
However, the code is not buggy. Just compare:
vma = vma_tmp;
if (vma_tmp->vm_start <= addr)
return vma;
with
munmap_back:
vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
if (vma && vma->vm_start < addr + len) {
if (do_munmap(mm, addr, len))
return -ENOMEM;
goto munmap_back;
}
Now, we know that addr + len does not wrap, and that len > 0, so we know
that this warning is incorrect. But it's not reasonable to expect gcc to
be able to deduce this.
See also the CERT warning threads recently on the GCC lists ;-)
--
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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