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

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Message-ID: <87mup2s8if.fsf@concordia.ellerman.id.au>
Date:   Wed, 19 Dec 2018 10:46:48 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     mwb@...ux.vnet.ibm.com,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        tlfalcon@...ux.vnet.ibm.com, minkim@...ibm.com,
        devicetree@...r.kernel.org,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] of: phandle_cache, fix refcounts, remove stale entry

Rob Herring <robh+dt@...nel.org> writes:
> 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.

I think it can wait to go into 4.21, it's not super critical and it's
not a regression since 4.19.

cheers