linux-kernel - [PATCH v3 0/2] of: phandle_cache, fix refcounts, remove stale entry

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Date:   Tue, 18 Dec 2018 11:40:01 -0800
From:   frowand.list@...il.com
To:     robh+dt@...nel.org, Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        Thomas Falcon <tlfalcon@...ux.vnet.ibm.com>,
        Juliet Kim <minkim@...ibm.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/2] of: phandle_cache, fix refcounts, remove stale entry

From: Frank Rowand <frank.rowand@...y.com>

Non-overlay dynamic devicetree node removal may leave the node in
the phandle cache.  Subsequent calls to of_find_node_by_phandle()
will incorrectly find the stale entry.  This bug exposed the foloowing
phandle cache refcount bug.

The refcount of phandle_cache entries is not incremented while in
the cache, allowing use after free error after kfree() of the
cached entry.

Changes since v2:
  - patch 2/2: add temporary variable np in __of_free_phandle_cache_entry()
    to improve readability
  - patch 2/2: explain reason for WARN_ON() in comment
  - patch 2/2: add Fixes tag in patch comment

Changes since v1:
  - make __of_free_phandle_cache() static
  - add WARN_ON(1) for unexpected condition in of_find_node_by_phandle()
  
Frank Rowand (2):
  of: of_node_get()/of_node_put() nodes held in phandle cache
  of: __of_detach_node() - remove node from phandle cache

 drivers/of/base.c       | 101 ++++++++++++++++++++++++++++++++++++------------
 drivers/of/dynamic.c    |   3 ++
 drivers/of/of_private.h |   4 ++
 3 files changed, 83 insertions(+), 25 deletions(-)

-- 
Frank Rowand <frank.rowand@...y.com>