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of: __of_detach_node() - remove node from phandle cache

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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: 0b3ce78e90 ("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>
This commit is contained in:
Frank Rowand 2018-12-18 11:40:03 -08:00 committed by Rob Herring
parent b8a9ac1a5b
commit 5801169a2e
3 changed files with 37 additions and 1 deletions
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31
drivers/of/base.c
View File

@ -169,6 +169,28 @@ 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;
@ -1214,11 +1236,18 @@ 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)) {
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);

3
drivers/of/dynamic.c
View File

@ -277,6 +277,9 @@ void __of_detach_node(struct device_node *np)
}
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);
}
/**

4
drivers/of/of_private.h
View File

@ -84,6 +84,10 @@ static inline void __of_detach_node_sysfs(struct device_node *np) {}
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);