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    SubjectRe: [PATCH 1/4] inet: Add skb_copy_datagram_iter
    On Sun, Nov 09, 2014 at 09:19:08PM +0000, Al Viro wrote:
    > [Michael Cc'd]
    >
    > On Fri, Nov 07, 2014 at 11:42:53PM +0000, Al Viro wrote:
    >
    > > I'll finish RTFS drivers/vhost and if it turns out to be OK I'll post the
    > > series moving those checks to the moment of copying iovec from userland,
    > > so that kernel-side we could always rely on ->msg_iov elements having been
    > > verified.
    >
    > Two questions:
    > 1) does sparc64 access_ok() need to differ for 32bit and 64bit tasks?
    > AFAICS, x86 and ppc just check that address is OK for 64bit process -
    > if a 32bit process passes the kernel an address that would be valid
    > for 64bit process, but not for 32bit one, we just get a pagefault in
    > __copy_from_user() and friends. No kernel objects are going to have
    > a virtual address in that range, so access_ok() doesn't bother preventing
    > such access attempts there...
    >
    > 2) shouldn't vhost_dev_cleanup() stop the worker thread before doing anything
    > else?
    > AFAICS, we do parts of vhost_dev teardown while the thread is
    > still running; granted, we keep dev->mm pinned down until after it stops
    > (or we would be _really_ screwed), but is it safe to do all those fput()s, etc.
    > while it's still running? Michael?

    Before invoking vhost_dev_cleanup,
    the caller for vhost-net (vhost_net_release) sets private data to NULL
    (using vhost_net_stop_vq) which guarantees thread will do nothing at all.
    vhost scsi does it in vhost_scsi_clear_endpoint.


    --
    MST


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