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of: overlay: do not free changeset when of_overlay_apply returns error

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New unittests for overlay notifiers reveal a memory leak in
of_overlay_apply() when a notifier returns an error for action
OF_OVERLAY_POST_APPLY.  The pr_err() message is:

   OF: ERROR: memory leak, expected refcount 1 instead of 3,
   of_node_get()/of_node_put() unbalanced - destroy cset entry: attach
   overlay node /testcase-data/overlay-node/test-bus/test-unittest17

Change the error path to no longer call free_overlay_changeset(),
and document that the caller of of_overlay_fdt_apply() may choose
to remove the overlay.

Update the unittest that triggered the error to expect the changed
return values and to call of_overlay_remove().

Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220502181742.1402826-4-frowand.list@gmail.com
This commit is contained in:
Frank Rowand 2022-05-02 13:17:42 -05:00 committed by Rob Herring
parent 992b0dc5c3
commit 421f4d14bc
2 changed files with 34 additions and 5 deletions
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29
drivers/of/overlay.c
View File

@ -952,6 +952,25 @@ out:
return ret;
}
/*
* of_overlay_fdt_apply() - Create and apply an overlay changeset
* @overlay_fdt: pointer to overlay FDT
* @overlay_fdt_size: number of bytes in @overlay_fdt
* @ret_ovcs_id: pointer for returning created changeset id
*
* Creates and applies an overlay changeset.
*
* See of_overlay_apply() for important behavior information.
*
* Return: 0 on success, or a negative error number. *@ret_ovcs_id is set to
* the value of overlay changeset id, which can be passed to of_overlay_remove()
* to remove the overlay.
*
* On error return, the changeset may be partially applied. This is especially
* likely if an OF_OVERLAY_POST_APPLY notifier returns an error. In this case
* the caller should call of_overlay_remove() with the value in *@ret_ovcs_id.
*/
int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
int *ret_ovcs_id)
{
@ -1019,15 +1038,19 @@ int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
ovcs->overlay_mem = overlay_mem;
ret = of_overlay_apply(ovcs);
if (ret < 0)
goto err_free_ovcs;
/*
* If of_overlay_apply() error, calling free_overlay_changeset() may
* result in a memory leak if the apply partly succeeded, so do NOT
* goto err_free_ovcs. Instead, the caller of of_overlay_fdt_apply()
* can call of_overlay_remove();
*/
mutex_unlock(&of_mutex);
of_overlay_mutex_unlock();
*ret_ovcs_id = ovcs->id;
return 0;
return ret;
err_free_ovcs:
free_overlay_changeset(ovcs);

10
drivers/of/unittest.c
View File

@ -2845,7 +2845,7 @@ static void __init of_unittest_overlay_notify(void)
EXPECT_END(KERN_INFO, "OF: overlay: overlay changeset pre-apply notifier error -16, target: /testcase-data/overlay-node/test-bus");
unittest(!ovcs_id, "ovcs_id created for overlay_16\n");
unittest(ovcs_id, "ovcs_id not created for overlay_16\n");
/* --- overlay 17 --- */
@ -2856,7 +2856,13 @@ static void __init of_unittest_overlay_notify(void)
EXPECT_END(KERN_INFO, "OF: overlay: overlay changeset post-apply notifier error -17, target: /testcase-data/overlay-node/test-bus");
unittest(!ovcs_id, "ovcs_id created for overlay_17\n");
unittest(ovcs_id, "ovcs_id not created for overlay_17\n");
if (ovcs_id) {
ret = of_overlay_remove(&ovcs_id);
unittest(!ret,
"overlay_17 of_overlay_remove(), ret = %d\n", ret);
}
/* --- overlay 18 --- */