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

On Tue, Dec 18, 2018 at 2:33 PM Frank Rowand [off-list ref] wrote:

On 12/18/18 12:09 PM, Frank Rowand wrote:

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On 12/18/18 12:01 PM, Rob Herring wrote:

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On Tue, Dec 18, 2018 at 12:57 PM Frank Rowand [off-list ref] wrote:

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On 12/17/18 2:52 AM, Michael Ellerman wrote:

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Hi Frank,

frowand.list@gmail.com writes:

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From: Frank Rowand <redacted>

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 <redacted>
Signed-off-by: Frank Rowand <redacted>
---

Similarly here can we add:

Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()")

Yes, thanks.

quoted

Cc: stable@vger.kernel.org # 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.

EOL shouldn't factor into it. There's always the possibility someone
else picks any kernel version.

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?

I think we just list v4.17 and be done with it.

Rob