Messages in this thread | | | Date | Wed, 15 Nov 2017 00:00:46 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP_WINDOW border |
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On Wed, 15 Nov 2017, Kirill A. Shutemov wrote: > On Tue, Nov 14, 2017 at 09:54:52PM +0100, Thomas Gleixner wrote: > > On Tue, 14 Nov 2017, Kirill A. Shutemov wrote: > > > > > On Tue, Nov 14, 2017 at 05:01:50PM +0100, Thomas Gleixner wrote: > > > > @@ -198,11 +199,14 @@ arch_get_unmapped_area_topdown(struct fi > > > > /* requesting a specific address */ > > > > if (addr) { > > > > addr = PAGE_ALIGN(addr); > > > > + if (!mmap_address_hint_valid(addr, len)) > > > > + goto get_unmapped_area; > > > > + > > > > > > Here and in hugetlb_get_unmapped_area(), we should align the addr after > > > the check, not before. Otherwise the alignment itself can bring us over > > > the borderline as we align up. > > > > Hmm, then I wonder whether the next check against vm_start_gap() which > > checks against the aligned address is correct: > > > > addr = PAGE_ALIGN(addr); > > vma = find_vma(mm, addr); > > > > if (end - len >= addr && > > (!vma || addr + len <= vm_start_gap(vma))) > > return addr; > > I think the check is correct. The check is against resulting addresses > that end up in vm_start/vm_end. In our case we want to figure out what > user asked for.
Well, but then checking just against the user supplied addr is only half of the story.
addr = boundary - PAGE_SIZE - PAGE_SIZE / 2; len = PAGE_SIZE - PAGE_SIZE / 2;
That fits, but then after alignment we end up with
addr = boudary - PAGE_SIZE;
and due to len > PAGE_SIZE this will result in a mapping which crosses the boundary, right? So checking against the PAGE_ALIGN(addr) should be the right thing to do.
Thanks,
tglx
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