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.
Rob
