4.20-stable review patch. If anyone has any objections, please let me know.
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From: Frank Rowand frank.rowand@sony.com
commit 5801169a2ed20003f771acecf3ac00574cf10a38 upstream.
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).
Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()") Reported-by: Michael Bringmann mwb@linux.vnet.ibm.com Cc: stable@vger.kernel.org # v4.17+ Signed-off-by: Frank Rowand frank.rowand@sony.com Signed-off-by: Rob Herring robh@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/of/base.c | 31 ++++++++++++++++++++++++++++++- drivers/of/dynamic.c | 3 +++ drivers/of/of_private.h | 4 ++++ 3 files changed, 37 insertions(+), 1 deletion(-)
--- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -162,6 +162,28 @@ 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; + struct device_node *np; + + if (!handle) + return; + + masked_handle = handle & phandle_cache_mask; + + if (phandle_cache) { + np = phandle_cache[masked_handle]; + if (np && handle == np->phandle) { + of_node_put(np); + phandle_cache[masked_handle] = NULL; + } + } +} + void of_populate_phandle_cache(void) { unsigned long flags; @@ -1209,11 +1231,18 @@ struct device_node *of_find_node_by_phan 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)) { + WARN_ON(1); /* did not uncache np on node removal */ + of_node_put(np); + phandle_cache[masked_handle] = NULL; + np = NULL; + } }
if (!np) { for_each_of_allnodes(np) - if (np->phandle == handle) { + if (np->phandle == handle && + !of_node_check_flag(np, OF_DETACHED)) { if (phandle_cache) { /* will put when removed from cache */ of_node_get(np); --- a/drivers/of/dynamic.c +++ b/drivers/of/dynamic.c @@ -268,6 +268,9 @@ void __of_detach_node(struct device_node }
of_node_set_flag(np, OF_DETACHED); + + /* race with of_find_node_by_phandle() prevented by devtree_lock */ + __of_free_phandle_cache_entry(np->phandle); }
/** --- a/drivers/of/of_private.h +++ b/drivers/of/of_private.h @@ -84,6 +84,10 @@ static inline void __of_detach_node_sysf int of_resolve_phandles(struct device_node *tree); #endif
+#if defined(CONFIG_OF_DYNAMIC) +void __of_free_phandle_cache_entry(phandle handle); +#endif + #if defined(CONFIG_OF_OVERLAY) void of_overlay_mutex_lock(void); void of_overlay_mutex_unlock(void);