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@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
