Commit 5e474817 authored Dec 05, 2017 by Geert Uytterhoeven Committed by Rob Herring Dec 06, 2017

of: overlay: Fix (un)locking in of_overlay_apply()



The special overlay mutex is taken first, hence it should be released
last in the error path.

of_resolve_phandles() must be called with of_mutex held.  Without it, a
node and new phandle could be added via of_attach_node(), making the max
phandle wrong.

free_overlay_changeset() must be called with of_mutex held, if any
non-trivial cleanup is to be done.

Hence move "mutex_lock(&of_mutex)" up, as suggested by Frank, and merge
the two tail statements of the success and error paths, now they became
identical.

Note that while the two mutexes are adjacent, we still need both:
__of_changeset_apply_notify(), which is called by __of_changeset_apply()
unlocks of_mutex, then does notifications then locks of_mutex.  So the
mutex get released in the middle of of_overlay_apply()

Fixes: f948d6d8 ("of: overlay: avoid race condition between applying multiple overlays")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>

parent 1352f09b

drivers/of/overlay.c

+5 −10

Original line number	Diff line number	Diff line
		@@ -706,12 +706,11 @@ int of_overlay_apply(struct device_node tree, int ovcs_id)
		}

		of_overlay_mutex_lock();
		mutex_lock(&of_mutex);

		ret = of_resolve_phandles(tree);
		if (ret)
		goto err_overlay_unlock;

		mutex_lock(&of_mutex);
		goto err_free_overlay_changeset;

		ret = init_overlay_changeset(ovcs, tree);
		if (ret)
		@@ -754,18 +753,14 @@ int of_overlay_apply(struct device_node tree, int ovcs_id)
		ret = ret_tmp;
		}

		mutex_unlock(&of_mutex);
		of_overlay_mutex_unlock();

		goto out;

		err_overlay_unlock:
		of_overlay_mutex_unlock();
		goto out_unlock;

		err_free_overlay_changeset:
		free_overlay_changeset(ovcs);

		out_unlock:
		mutex_unlock(&of_mutex);
		of_overlay_mutex_unlock();

		out:
		pr_debug("%s() err=%d\n", __func__, ret);

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