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7c528e457d
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@kernel.org> Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.