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    SubjectRe: [PATCH] vfs: fix IMA lockdep circular locking dependency
    On Tue, May 15, 2012 at 05:45:44PM -0700, Linus Torvalds wrote:
    > On Tue, May 15, 2012 at 5:42 PM, Al Viro <> wrote:
    > >
    > > Er... ?Looks like you forgot to actually put the patch in there ;-)
    > Oops. Err.. I meant to do that. Right. To check that you're awake.

    Frankly, I would split it in two - one introducing security_mmap_addr()
    and converting the callers, and another doing the rest of it.

    Said that, I'm not sure I like the resulting picture.

    1) caller in __bprm_mm_init() is simply ridiculous - note that
    arguments are bleeding *constants*, so it might very well have
    been a BUG_ON(). If it fails, you'll have every execve() fail.

    2) get_unmapped_area() probably ought to grow such a caller and
    I really suspect that it would've killed quite a few of them.

    3) expand_downwards() seems to be missing the basic sanity checks on the
    validity of VMA range (arch_mmap_check(), that is). itanic opencodes
    the equivalent before calling expand_stack(); arm and mn10300 do not
    bother, which might or might not be legitimate - depends on whether
    one can get a fault in the first page *and* reach the check_stack:
    in e.g. arm __do_page_fault(). Which just might be possible, if attacker
    maps something just above said first page with MAP_GROWSDOWN and
    tries to write at very small address - IIRC, the first page on arm
    contains the stuff that shouldn't be world-writable... s390 doesn't
    care and I'm not sure about sparc32/sparc64 - it looks like that shouldn't
    be possible to hit, but...

    4) i810_dma.c ought to be switched to vm_mmap() - as discussed in that
    thread back then, magical mystery wank with ->f_op reassignments does
    not rely on ->mmap_sem for protection and thus can be taken out of
    under ->mmap_sem.

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