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Re: [PATCH] vfs: check i_count under lock in evict_inodes

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On Mon, Jul 11, 2016 at 05:15:04PM -0700, Chunwei Chen wrote:
> We need to check i_count again with i_lock held, because iput might re-add
> i_count when lazytime is on. Without this check, we could end up with
> double-free or use-after-free.

Details, please.  Ideally - with a reproducer.  Who is calling that iput()
at that point of generic_shutdown_super() (has to be another thread) and
just what will happen if the same iput() is delayed until *after*
evict_inodes(), all the way into ->put_super().  At which point there's
no promise whatsoever that the data structures used by ->evict_inode()
hadn't been already freed...

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[PATCH] vfs: check i_count under lock in evict_inodes Chunwei Chen <david.chen@osnexus.com> - 2016-07-12 02:30 +0200
  Re: [PATCH] vfs: check i_count under lock in evict_inodes Al Viro <viro@ZenIV.linux.org.uk> - 2016-07-12 02:50 +0200
    Re: [PATCH] vfs: check i_count under lock in evict_inodes David Chen <david.chen@osnexus.com> - 2016-07-12 03:40 +0200
      Re: [PATCH] vfs: check i_count under lock in evict_inodes Christoph Hellwig <hch@infradead.org> - 2016-07-12 03:50 +0200
      Re: [PATCH] vfs: check i_count under lock in evict_inodes Al Viro <viro@ZenIV.linux.org.uk> - 2016-07-12 07:30 +0200

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