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SubjectRe: [PATCH v4 02/18] of: overlay: add missing of_node_put() after add new node to changeset
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On 10/18/18 10:05, Rob Herring wrote:
> On Mon, Oct 15, 2018 at 07:37:22PM -0700, frowand.list@gmail.com wrote:
>> From: Frank Rowand <frank.rowand@sony.com>
>>
>> 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
>
> Same comment on formatting.

OK.


>>
>> 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)
>>
>> Signed-off-by: Frank Rowand <frank.rowand@sony.com>
>> ---
>> 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 <frank.rowand@sony.com>
>>
>

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