On 10/18/18 10:05, Rob Herring wrote: > On Mon, Oct 15, 2018 at 07:37:22PM -0700, frowand.list@xxxxxxxxx wrote: >> 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 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@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 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@xxxxxxxx> >> >
