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Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t

From David Howells <dhowells@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t
Date 2017-02-24 15:30 +0100
Message-ID <tep2F-1r4-3@gated-at.bofh.it> (permalink)
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Kees Cook <keescook@chromium.org> wrote:

> We can't allow the increment from 0 since it violates the intended
> use-after-free protections.

I would have thought that the protections would've been against the carry flag
getting set.

> If "0" means "still valid" then this
> sounds like it needs a global +1, as Elena suggested in her reply.

This makes it sound like refcount_t is then unsuitable for this.

Since I want to overhaul the code to use more RCU and eliminate some of the
locking, it might be worth waiting on the patches.

David

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[PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t Elena Reshetova <elena.reshetova@intel.com> - 2017-02-21 16:50 +0100
  Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t David Howells <dhowells@redhat.com> - 2017-02-22 17:20 +0100
    RE: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-22 18:30 +0100
      Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t Kees Cook <keescook@chromium.org> - 2017-02-22 18:40 +0100
        RE: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to  refcount_t "Reshetova, Elena" <elena.reshetova@intel.com> - 2017-02-23 14:40 +0100
        Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t David Howells <dhowells@redhat.com> - 2017-02-24 15:30 +0100
      Re: [PATCH 1/4] fs, afs: convert afs_cell.usage from atomic_t to refcount_t David Howells <dhowells@redhat.com> - 2017-02-22 18:40 +0100

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