Re: [PATCH v4 01/18] of: overlay: add tests to validate kfrees from overlay removal
From: Alan Tull <atull@kernel.org>
Date: 2018-10-17 21:30:54
Also in:
linux-devicetree, linux-fpga, lkml
On Mon, Oct 15, 2018 at 9:39 PM [off-list ref] wrote: Hi Frank,
quoted hunk ↗ jump to hunk
From: Frank Rowand <redacted> 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@100/hvac-medium-2 expected refcount 1 instead of 2. of_node_get() / of_node_put() are unbalanced for this node. Signed-off-by: Frank Rowand <redacted> --- 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)) { + /* 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));
Still testing as much as I have time to do.
I'm hitting this error message once when removing an overlay that adds
several child nodes. The only node I get the message for was a node
that added a fixed-clock (the other nodes didn't trigger the error).
Then even if I edited all the rest of the overlay DTS and removed all
other child nodes and all references to the clock from other nodes, I
still got the error.
Removing dtbo: 1-socfpga_arria10_socdk_sdmmc_ghrd_ovl_ext_cfg.dtb
[ 72.032270] OF: ERROR: memory leak - destroy cset entry: attach
overlay node /soc/base_fpga_region/clk_0 expected refcount 1 instead
of 2. of_node_get() / of_node_put() are unbalanced for this node.
Here's the very stripped down overlay:
/dts-v1/;
/plugin/;
/ {
fragment@0 {
target-path = "/soc/base_fpga_region";
#address-cells = <1>;
#size-cells = <1>;
__overlay__ {
external-fpga-config;
#address-cells = <1>;
#size-cells = <1>;
clk_0: clk_0 {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <100000000>; /* 100.00 MHz */
clock-output-names = "clk_0-clk";
};
};
};
};
I'll look at it some more tomorrow and try to figure out what's
special about this node.
Alan
quoted hunk ↗ jump to hunk
+ } 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 [off-list ref]