[lkml]   [2018]   [Oct]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH v3 02/18] of: overlay: add missing of_node_put() after add new node to changeset
From: Frank Rowand <>

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 of_node_release() overlay node /testcase-data/overlay-node/test-bus/test-unittest4 before free overlay changeset

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

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)

Signed-off-by: Frank Rowand <>
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 1176cb4b6e4e..32cfee68f2e3 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 <>
 \ /
  Last update: 2018-10-15 02:28    [W:0.161 / U:2.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site