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    SubjectRe: access_ok macor
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    On Tuesday 14 July 2009, Michal Simek wrote:
    > Arnd Bergmann wrote:

    > >> r29=00000000, r30=00000000, r31=CE9759A4, rPC=C000123C
    > >> msr=800045AE, ear=00000001, esr=000000B2, fsr=000080D0
    > >> Segmentation fault
    > >>
    > >
    > > I guess then you should check if 0xc000123c is in your
    > > exception table, or why it is not.
    >
    > on that address is load instruction for unaligned exception because addr is odd number
    > that's why is called unaligned exception handler and from this function
    > is called load instruction which failed. :-(
    >
    > Currently this make more sense why that tests failed. If that pointers are
    > even number exception is not taken and exception sure don't have fixup for it because
    > this is generic code. :-(
    >
    > That's the problem because we are looking for regs->pc but this point to unaligned exception
    > handler.

    Ok, that makes a lot of sense.

    The solution then is to handle fixups from the unaligned exception handler
    if you come from the kernel. That should fix the three text cases.

    I don't fully understand your exception handling there, but I think you
    also need to add code checking for __range_ok() to your unaligned handler,
    to prevent malicious user space code from accessing the kernel through
    unaligned pointers.

    Arnd <><


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