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    SubjectRe: [FYI] tux3: Core changes
    On Tue 26-05-15 19:22:39, Sergey Senozhatsky wrote:
    > On (05/26/15 01:08), Daniel Phillips wrote:
    > > On Tuesday, May 26, 2015 12:09:10 AM PDT, Jan Kara wrote:
    > > > E.g. video drivers (or infiniband or direct IO for that matter) which
    > > >have buffers in user memory (may be mmapped file), grab references to pages
    > > >and hand out PFNs of those pages to the hardware to store data in them...
    > > >If you fork a page after the driver has handed PFNs to the hardware, you've
    > > >just lost all the writes hardware will do.
    > >
    > > Hi Jan,
    > >
    > > The page forked because somebody wrote to it with write(2) or mmap write at
    > > the same time as a video driver (or infiniband or direct IO) was doing io to
    > > it. Isn't the application trying hard to lose data in that case? It would
    > > not need page fork to lose data that way.
    > >
    >
    > Hello,
    >
    > is it possible to page-fork-bomb the system by some 'malicious' app?
    Well, you can have only two copies of each page - the one under writeout
    and the one in page cache. Furthermore you are limited by dirty throttling
    so I don't think this would allow any out-of-ordinary DOS vector...

    Honza
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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