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RE: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t

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> On Tue, Feb 21, 2017 at 05:49:01PM +0200, Elena Reshetova wrote:
> > refcount_t type and corresponding API should be
> > used instead of atomic_t when the variable is used as
> > a reference counter. This allows to avoid accidental
> > refcounter overflows that might lead to use-after-free
> > situations.
> 
> I'm missing something: how do you overflow a log item object
> reference count?

We are currently converting all reference counters present in kernel to a safer refcount_t type. 
Agreed, in some cases it might be easier or harder to actually create/trigger an overflow, but since it can be caused even by a bug in the legitimate code (current version or its future iterative), it is good idea to do "safe defaults" and stop worrying about the problem. 

Do you have any reasons why it should not be converted? 

Best Regards,
Elena.
> 
> Cheers,
> 
> Dave.
> --
> Dave Chinner
> david@fromorbit.com

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[PATCH 0/7] fs, xfs subsystem refcounter conversions Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:50 +0100
  [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:50 +0100
    Re: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-02-21 17:40 +0100
      RE: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 12:20 +0100
    Re: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t Dave Chinner <david@fromorbit.com> - 2017-02-22 00:00 +0100
      RE: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 12:30 +0100
        Re: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t Dave Chinner <david@fromorbit.com> - 2017-02-22 23:10 +0100
          RE: [PATCH 1/7] fs, xfs: convert xfs_bui_log_item.bui_refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-23 09:00 +0100
  [PATCH 5/7] fs, xfs: convert xlog_ticket.t_ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100
  Re: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-02-21 17:00 +0100
    RE: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-21 17:10 +0100
      Re: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-02-21 17:30 +0100
        Re: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-02-21 17:40 +0100
      Re: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-02-21 18:10 +0100
        Re: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t Brian Foster <bfoster@redhat.com> - 2017-02-21 20:30 +0100
          RE: [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from  atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 12:30 +0100
  [PATCH 7/7] fs, xfs: convert xfs_rui_log_item.rui_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100
  [PATCH 4/7] fs, xfs: convert xfs_efi_log_item.efi_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100
  [PATCH 3/7] fs, xfs: convert xfs_buf_log_item.bli_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100
  [PATCH 2/7] fs, xfs: convert xfs_buf.b_hold and xfs_buf.b_lru_ref from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100
    Re: [PATCH 2/7] fs, xfs: convert xfs_buf.b_hold and  xfs_buf.b_lru_ref from atomic_t to refcount_t Peter Zijlstra <peterz@infradead.org> - 2017-02-21 17:10 +0100
      Re: [PATCH 2/7] fs, xfs: convert xfs_buf.b_hold and  xfs_buf.b_lru_ref from atomic_t to refcount_t Dave Chinner <david@fromorbit.com> - 2017-02-22 00:00 +0100
        RE: [PATCH 2/7] fs, xfs: convert xfs_buf.b_hold and  xfs_buf.b_lru_ref from atomic_t to refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 12:20 +0100
  [PATCH 6/7] fs, xfs: convert xfs_cui_log_item.cui_refcount from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 17:00 +0100

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