Re: [PATCH v03] powerpc/mobility: Fix node detach/rename problem

On 12/12/2018 08:57 PM, Michael Ellerman wrote:

Frank Rowand [off-list ref] writes:

quoted

On 12/11/18 8:07 AM, Rob Herring wrote:

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On Tue, Dec 11, 2018 at 7:29 AM Michael Ellerman [off-list ref] wrote:

...

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diff --git a/drivers/of/base.c b/drivers/of/base.c
index 09692c9b32a7..d8e4534c0686 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c

@@ -1190,6 +1190,10 @@ struct device_node *of_find_node_by_phandle(phandle handle)
                if (phandle_cache[masked_handle] &&
                    handle == phandle_cache[masked_handle]->phandle)
                        np = phandle_cache[masked_handle];
+
+               /* If we find a detached node, remove it */
+               if (of_node_check_flag(np, OF_DETACHED))
+                       np = phandle_cache[masked_handle] = NULL;

The bug you found exposes a couple of different issues, a little bit
deeper than the proposed fix.  I'll work on a fuller fix tonight or
tomorrow.

OK thanks.

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I'm wondering if we should explicitly remove the node from the cache
when we set OF_DETACHED. Otherwise, it could be possible that the node
pointer has been freed already. Or maybe we need both?

Yes, it should be explicitly removed.  I may also add in a paranoia check in
of_find_node_by_phandle().

That seems best to me.

I agree that we should do both.

cheers

Michael

-- 
Michael W. Bringmann
Linux I/O, Networking and Security Development
IBM Corporation
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