Re: [PATCH v2 2/2] of: __of_detach_node() - remove node from phandle cache

From: Frank Rowand
Date: Tue Dec 18 2018 - 15:33:23 EST

On 12/18/18 12:09 PM, Frank Rowand wrote:
> On 12/18/18 12:01 PM, Rob Herring wrote:
>> On Tue, Dec 18, 2018 at 12:57 PM Frank Rowand <frowand.list@xxxxxxxxx> wrote:
>>> On 12/17/18 2:52 AM, Michael Ellerman wrote:
>>>> Hi Frank,
>>>> frowand.list@xxxxxxxxx writes:
>>>>> From: Frank Rowand <frank.rowand@xxxxxxxx>
>>>>> 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. Remove the node from the
>>>>> cache.
>>>>> Add paranoia checks in of_find_node_by_phandle() as a second level
>>>>> of defense (do not return cached node if detached, do not add node
>>>>> to cache if detached).
>>>>> Reported-by: Michael Bringmann <mwb@xxxxxxxxxxxxxxxxxx>
>>>>> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx>
>>>>> ---
>>>> Similarly here can we add:
>>>> Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()")
>>> Yes, thanks.
>>>> Cc: stable@xxxxxxxxxxxxxxx # v4.17+
>>> Nope, 0b3ce78e90fc does not belong in stable (it is a feature, not a bug
>>> fix). So the bug will not be in stable.
>> 0b3ce78e90fc landed in v4.17, so Michael's line above is correct.
>> Annotating it with 4.17 only saves Greg from trying and then emailing
>> us to backport this patch as it wouldn't apply.
> Thanks for the correction. I was both under-thinking and over-thinking,
> ending up with an incorrect answer.
> Can you add the Cc: to version 3 patch comments (both 1/2 and 2/2) or do
> you want me to re-spin?

Now that my thinking has been straightened out, a little bit more checking
for the other pre-requisite patches show:

v4.18: commit b9952b5218ad ("of: overlay: update phandle cache on overlay apply and remove")
v4.19: commit e54192b48da7 ("of: fix phandle cache creation for DTs with no phandles")

These can be addressed by changing the "Cc:" to ... # v4.19+
because stable v4.17.* and v4.18.* are end of life.

Or the pre-requisites can be listed:

# v4.17: b9952b5218ad of: overlay: update phandle cache
# v4.17: e54192b48da7 of: fix phandle cache creation
# v4.17

# v4.18: e54192b48da7 of: fix phandle cache creation
# v4.18

# v4.19+

Do you have a preference?

> -Frank
>> Rob