From: Frank Rowand <frank.rowand@xxxxxxxx> The refcount of a newly added overlay node decrements to one (instead of zero) when the overlay changeset is destroyed. This change will cause the final decrement be to zero. After applying this patch, new validation warnings will be reported from the devicetree unittest during boot due to a pre-existing devicetree bug. The warnings will be similar to: OF: ERROR: memory leak before free overlay changeset, /testcase-data/overlay-node/test-bus/test-unittest4 This pre-existing devicetree bug will also trigger a WARN_ONCE() from refcount_sub_and_test_checked() when an overlay changeset is destroyed without having first been applied. This scenario occurs when an error in the overlay is detected during the overlay changeset creation: WARNING: CPU: 0 PID: 1 at lib/refcount.c:187 refcount_sub_and_test_checked+0xa8/0xbc refcount_t: underflow; use-after-free. (unwind_backtrace) from (show_stack+0x10/0x14) (show_stack) from (dump_stack+0x6c/0x8c) (dump_stack) from (__warn+0xdc/0x104) (__warn) from (warn_slowpath_fmt+0x44/0x6c) (warn_slowpath_fmt) from (refcount_sub_and_test_checked+0xa8/0xbc) (refcount_sub_and_test_checked) from (kobject_put+0x24/0x208) (kobject_put) from (of_changeset_destroy+0x2c/0xb4) (of_changeset_destroy) from (free_overlay_changeset+0x1c/0x9c) (free_overlay_changeset) from (of_overlay_remove+0x284/0x2cc) (of_overlay_remove) from (of_unittest_apply_revert_overlay_check.constprop.4+0xf8/0x1e8) (of_unittest_apply_revert_overlay_check.constprop.4) from (of_unittest_overlay+0x960/0xed8) (of_unittest_overlay) from (of_unittest+0x1cc4/0x2138) (of_unittest) from (do_one_initcall+0x4c/0x28c) (do_one_initcall) from (kernel_init_freeable+0x29c/0x378) (kernel_init_freeable) from (kernel_init+0x8/0x110) (kernel_init) from (ret_from_fork+0x14/0x2c) Tested-by: Alan Tull <atull@xxxxxxxxxx> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx> --- drivers/of/overlay.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c index f5fc8859a7ee..7613f7d680c7 100644 --- a/drivers/of/overlay.c +++ b/drivers/of/overlay.c @@ -379,7 +379,9 @@ static int add_changeset_node(struct overlay_changeset *ovcs, if (ret) return ret; - return build_changeset_next_level(ovcs, tchild, node); + ret = build_changeset_next_level(ovcs, tchild, node); + of_node_put(tchild); + return ret; } if (node->phandle && tchild->phandle) -- Frank Rowand <frank.rowand@xxxxxxxx>
