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    SubjectRe: [PATCH] mm: usercopy: move the virt_addr_valid() below the is_vmalloc_addr()
    On Mon, May 09, 2022 at 08:37:32PM -0700, Andrew Morton wrote:
    > Matthew & Kees,
    >
    > On Thu, 5 May 2022 07:10:37 +0000 Yuanzheng Song <songyuanzheng@huawei.com> wrote:
    >
    > > The is_kmap_addr() and the is_vmalloc_addr() in the check_heap_object()
    > > will not work, because the virt_addr_valid() will exclude the kmap and
    > > vmalloc regions. So let's move the virt_addr_valid() below
    > > the is_vmalloc_addr().
    >
    > The author,
    >
    > > Signed-off-by: Yuanzheng Song <songyuanzheng@huawei.com>
    >
    > Tells me off-list that this fix:
    >
    > > --- a/mm/usercopy.c
    > > +++ b/mm/usercopy.c
    > > @@ -163,9 +163,6 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
    > > {
    > > struct folio *folio;
    > >
    > > - if (!virt_addr_valid(ptr))
    > > - return;
    > > -
    > > if (is_kmap_addr(ptr)) {
    > > unsigned long page_end = (unsigned long)ptr | (PAGE_SIZE - 1);
    > >
    > > @@ -190,6 +187,9 @@ static inline void check_heap_object(const void *ptr, unsigned long n,
    > > return;
    > > }
    > >
    > > + if (!virt_addr_valid(ptr))
    > > + return;
    > > +
    > > folio = virt_to_folio(ptr);
    > >
    > > if (folio_test_slab(folio)) {
    >
    > is required to fix patches "mm/usercopy: Check kmap addresses properly"
    > and "mm/usercopy: Detect vmalloc overruns".

    Ah, this very well may be true! I will need to study this (or more
    likely, I will build some selftests), but I suspect willy knows off the
    top of his head. :)

    --
    Kees Cook

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