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Subject[PATCH 4.19 143/148] of: __of_detach_node() - remove node from phandle cache
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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
@@ -161,6 +161,28 @@ 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;
@@ -1169,11 +1191,18 @@ 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
@@ -76,6 +76,10 @@ 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);

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