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    SubjectRe: [PATCHES] uaccess comedi compat
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    On 29/05/2020 01:34, Al Viro wrote:
    > The way comedi compat ioctls are done is wrong.
    > Instead of having ->compat_ioctl() copying the 32bit
    > stuff in, then passing the kernel copies to helpers shared
    > with native ->ioctl() and doing copyout with conversion if
    > needed, it's playing silly buggers with creating a 64bit
    > copy on user stack, then calling native ioctl (which copies
    > that copy into the kernel), then fetching it from user stack,
    > converting to 32bit variant and copying that to user.
    > Extra headache for no good reason. And the single
    > largest remaining pile of __put_user()/__get_user() this side
    > of arch/*. IMO compat_alloc_user_space() should die...
    >
    > NOTE: this is only compile-tested - I simply don't
    > have the hardware in question.
    >
    > Anyway, the branch lives in #uaccess.comedi, based
    > at v5.7-rc1
    >
    > Al Viro (10):
    > comedi: move compat ioctl handling to native fops
    > comedi: get rid of indirection via translated_ioctl()
    > comedi: get rid of compat_alloc_user_space() mess in COMEDI_CHANINFO compat
    > comedi: get rid of compat_alloc_user_space() mess in COMEDI_RANGEINFO compat
    > comedi: get rid of compat_alloc_user_space() mess in COMEDI_INSN compat
    > comedi: get rid of compat_alloc_user_space() mess in COMEDI_INSNLIST compat
    > comedi: lift copy_from_user() into callers of __comedi_get_user_cmd()
    > comedi: do_cmdtest_ioctl(): lift copyin/copyout into the caller
    > comedi: do_cmd_ioctl(): lift copyin/copyout into the caller
    > comedi: get rid of compat_alloc_user_space() mess in COMEDI_CMD{,TEST} compat

    There is a bug in patch 05. Patch 10 doesn't seem to have been sent yet
    (I didn't receive it and I can't see it in the thread in the LKML
    archives). I've signed off on 01-04, 06-09.

    These should be Cc'd to Greg KH and to devel@driverdev.osuosl.org.

    Cheers,
    Ian

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