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Message-ID: <20181018170303.GA15557@bogus>
Date: Thu, 18 Oct 2018 12:03:03 -0500
From: Rob Herring <robh@...nel.org>
To: frowand.list@...il.com
Cc: Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Alan Tull <atull@...nel.org>, Moritz Fischer <mdf@...nel.org>,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
devicetree@...r.kernel.org, linux-fpga@...r.kernel.org
Subject: Re: [PATCH v4 01/18] of: overlay: add tests to validate kfrees from
overlay removal
On Mon, Oct 15, 2018 at 07:37:21PM -0700, frowand.list@...il.com wrote:
> From: Frank Rowand <frank.rowand@...y.com>
>
> Add checks:
> - attempted kfree due to refcount reaching zero before overlay
> is removed
> - properties linked to an overlay node when the node is removed
> - node refcount > one during node removal in a changeset destroy,
> if the node was created by the changeset
>
> After applying this patch, several validation warnings will be
> reported from the devicetree unittest during boot due to
> pre-existing devicetree bugs. The warnings will be similar to:
>
> OF: ERROR: of_node_release() overlay node /testcase-data/overlay-node/test-bus/test-unittest11/test-unittest111 contains unexpected properties
> OF: ERROR: memory leak - destroy cset entry: attach overlay node /testcase-data-2/substation@.../hvac-medium-2 expected refcount 1 instead of 2. of_node_get() / of_node_put() are unbalanced for this node.
These messages could be formatted more consistently. Put the path either
at the beginning (after any prefix) or end. Beginning is more like a
compiler error. End puts what the problem is before it's off the edge of
the screen.
> Signed-off-by: Frank Rowand <frank.rowand@...y.com>
> ---
> Changes since v3:
> - Add expected value of refcount for destroy cset entry error. Also
> explain the cause of the error.
>
> drivers/of/dynamic.c | 29 +++++++++++++++++++++++++++++
> drivers/of/overlay.c | 1 +
> include/linux/of.h | 15 ++++++++++-----
> 3 files changed, 40 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> index f4f8ed9b5454..24c97b7a050f 100644
> --- a/drivers/of/dynamic.c
> +++ b/drivers/of/dynamic.c
> @@ -330,6 +330,25 @@ void of_node_release(struct kobject *kobj)
> if (!of_node_check_flag(node, OF_DYNAMIC))
> return;
>
> + if (of_node_check_flag(node, OF_OVERLAY)) {
> +
> + if (!of_node_check_flag(node, OF_OVERLAY_FREE_CSET)) {
I worry the flags are getting unwieldy.
> + /* premature refcount of zero, do not free memory */
> + pr_err("ERROR: memory leak %s() overlay node %pOF before free overlay changeset\n",
> + __func__, node);
> + return;
> + }
> +
> + /*
> + * If node->properties non-empty then properties were added
> + * to this node either by different overlay that has not
> + * yet been removed, or by a non-overlay mechanism.
> + */
> + if (node->properties)
> + pr_err("ERROR: %s() overlay node %pOF contains unexpected properties\n",
> + __func__, node);
> + }
> +
> property_list_free(node->properties);
> property_list_free(node->deadprops);
>
> @@ -434,6 +453,16 @@ struct device_node *__of_node_dup(const struct device_node *np,
>
> static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
> {
> + if (ce->action == OF_RECONFIG_ATTACH_NODE &&
> + of_node_check_flag(ce->np, OF_OVERLAY)) {
> + if (kref_read(&ce->np->kobj.kref) > 1) {
> + pr_err("ERROR: memory leak - destroy cset entry: attach overlay node %pOF expected refcount 1 instead of %d. of_node_get() / of_node_put() are unbalanced for this node.\n",
> + ce->np, kref_read(&ce->np->kobj.kref));
> + } else {
> + of_node_set_flag(ce->np, OF_OVERLAY_FREE_CSET);
> + }
> + }
> +
> of_node_put(ce->np);
> list_del(&ce->node);
> kfree(ce);
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index eda57ef12fd0..1176cb4b6e4e 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -373,6 +373,7 @@ static int add_changeset_node(struct overlay_changeset *ovcs,
> return -ENOMEM;
>
> tchild->parent = target_node;
> + of_node_set_flag(tchild, OF_OVERLAY);
>
> ret = of_changeset_attach_node(&ovcs->cset, tchild);
> if (ret)
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 4d25e4f952d9..aa1dafaec6ae 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -138,11 +138,16 @@ static inline void of_node_put(struct device_node *node) { }
> extern struct device_node *of_stdout;
> extern raw_spinlock_t devtree_lock;
>
> -/* flag descriptions (need to be visible even when !CONFIG_OF) */
> -#define OF_DYNAMIC 1 /* node and properties were allocated via kmalloc */
> -#define OF_DETACHED 2 /* node has been detached from the device tree */
> -#define OF_POPULATED 3 /* device already created for the node */
> -#define OF_POPULATED_BUS 4 /* of_platform_populate recursed to children of this node */
> +/*
> + * struct device_node flag descriptions
> + * (need to be visible even when !CONFIG_OF)
> + */
> +#define OF_DYNAMIC 1 /* (and properties) allocated via kmalloc */
> +#define OF_DETACHED 2 /* detached from the device tree */
> +#define OF_POPULATED 3 /* device already created */
> +#define OF_POPULATED_BUS 4 /* platform bus created for children */
> +#define OF_OVERLAY 5 /* allocated for an overlay */
> +#define OF_OVERLAY_FREE_CSET 6 /* in overlay cset being freed */
>
> #define OF_BAD_ADDR ((u64)-1)
>
> --
> Frank Rowand <frank.rowand@...y.com>
>
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