linux-kernel - Re: [PATCH v2 0/2] of: phandle_cache, fix refcounts, remove stale entry

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Date:   Tue, 18 Dec 2018 09:43:07 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     mwb@...ux.vnet.ibm.com,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        tlfalcon@...ux.vnet.ibm.com, minkim@...ibm.com,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] of: phandle_cache, fix refcounts, remove stale entry

On Mon, Dec 17, 2018 at 1:56 AM <frowand.list@...il.com> wrote:
>
> 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 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

I'll send this to Linus this week if I get a tested by. Otherwise, it
will go in for 4.21.

Rob