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    SubjectRe: [PATCH 0/9] overlay: fix inconsistency of ro file after copy-up
    On Sun, Feb 19, 2017 at 10:14 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:

    > This is one hell of a DoS vector - it's really easy to eat tons of struct
    > file that way. Preparatory parts of that series make sense on their own,
    > but your "let's allocate a struct file, call ->open() and schedule that
    > struct file for closing upon the exit to userland on each kernel_read()"
    > is not.

    Found a couple of instances of this pattern (haven't looked very hard,
    possibly there's more):

    nfsd_read()
    cachefiles_write_page()

    How come this hasn't been a problem for them?

    Would flush_delayed_fput() work here? I couldn't really find what the
    locking issues with synchronous fputs were.

    Thanks,
    Miklos

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