On 12/14/18 1:56 PM, Michael Bringmann wrote:
> On 12/14/2018 11:20 AM, Rob Herring wrote:
>> On Fri, Dec 14, 2018 at 12:43 AM <frowand.list@xxxxxxxxx> wrote:
>>>
>>> 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>
>>> ---
>>> drivers/of/base.c | 29 ++++++++++++++++++++++++++++-
>>> drivers/of/dynamic.c | 3 +++
>>> drivers/of/of_private.h | 4 ++++
>>> 3 files changed, 35 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>>> index d599367cb92a..34a5125713c8 100644
>>> --- a/drivers/of/base.c
>>> +++ b/drivers/of/base.c
>>> @@ -162,6 +162,27 @@ int of_free_phandle_cache(void)
>>> late_initcall_sync(of_free_phandle_cache);
>>> #endif
>>>
>>> +/*
>>> + * Caller must hold devtree_lock.
>>> + */
>>> +void __of_free_phandle_cache_entry(phandle handle)
>>> +{
>>> + phandle masked_handle;
>>> +
>>> + if (!handle)
>>> + return;
>>> +
>>> + masked_handle = handle & phandle_cache_mask;
>>> +
>>> + if (phandle_cache) {
>>> + if (phandle_cache[masked_handle] &&
>>> + handle == phandle_cache[masked_handle]->phandle) {
>>> + of_node_put(phandle_cache[masked_handle]);
>>> + phandle_cache[masked_handle] = NULL;
>>> + }
>>> + }
>>> +}
>>> +
>>> void of_populate_phandle_cache(void)
>>> {
>>> unsigned long flags;
>>> @@ -1209,11 +1230,17 @@ 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 (np && of_node_check_flag(np, OF_DETACHED)) {
>>> + of_node_put(np);
>>> + phandle_cache[masked_handle] = NULL;
>>
>> This should never happen, right? Any time we set OF_DETACHED, the
>> entry should get removed from the cache. I think we want a WARN here
>> in case we're in an unexpected state.
Correct, this should never happen. I will add the WARN.
> We don't actually remove the pointer from the phandle cache when we set
> OF_DETACHED in drivers/of/dynamic.c:__of_detach_node. The phandle cache
> is currently static within drivers/of/base.c. There are a couple of
> calls to of_populate_phandle_cache / of_free_phandle_cache within
> drivers/of/overlay.c, but these are not involved in the device tree
> updates that occur during LPAR migration. A WARN here would only make
> sense, if we also arrange to clear the handle.
Rob's reply did not include the full patch 2/2. The full patch 2/2 also
adds a call to __of_free_phandle_cache_entry() in __of_detach_node().
-Frank
>
>>
>> Rob
>
> Michael
>
>>
>>
>
