Hi Nishka,
On 15-08-19 08:00, Nishka Dasgupta wrote:
Each iteration of for_each_child_of_node puts the previous node, but
in the case of a goto from the middle of the loop, there is no put,
thus causing a memory leak. Add an of_node_put before three such goto
statements.
Issue found with Coccinelle.
Signed-off-by: Nishka Dasgupta <nishkadg.linux@xxxxxxxxx>
Thank you for your patch.
I do not like doing an of_node_put for something which we did not
explicitly of_node_get. So I was thinking about maybe replacing the
goto-s with a break.
But even if we put a break in the for_each_child_of_node loop,
we still leak the reference. Which IMHO means that the semantics of
the for_each_child_of_node helper are broken, this certainly violates
the principle of least surprise which one would expect of a good API.
I see that there are quite a few callers of this function:
[hans@shalem linux]$ ack -l for_each_child_of_node drivers | wc -l
194
And doing a manual check of these (with the intend to stop after
a couple) I already find something suspicious in the second file
ack -l returns:
for_each_child_of_node(parent, dn) {
pnv_php_detach_device_nodes(dn);
of_node_put(dn);
refcount = kref_read(&dn->kobj.kref);
if (refcount != 1)
pr_warn("Invalid refcount %d on <%pOF>\n",
refcount, dn);
of_detach_node(dn);
}
note this does an of_node_put itself and then continues iterating,
now this function looks pretty magical to me, so it might be fine...
4th file inspected, same issue with error returns as the libahci_platform
code, see drivers/pci/controller/pci-tegra.c: tegra_pcie_parse_dt
also should that function not do a a get on the node since it stores
it in rp->np if things do succeed ?
5th file: drivers/char/rtc.c:
for_each_node_by_name(ebus_dp, "ebus") {
struct device_node *dp;
for_each_child_of_node(ebus_dp, dp) {
if (of_node_name_eq(dp, "rtc")) {
op = of_find_device_by_node(dp);
if (op) {
rtc_port = op->resource[0].start;
rtc_irq = op->irqs[0];
goto found;
}
}
}
}
Also a leak AFAICT.
10th file: drivers/phy/phy-core.c:
for_each_child_of_node(phy_provider->children, child)
if (child == node)
return phy_provider;
Another leak...
I'm going to stop now because this just aint funny, but I do believe this
nicely illustrates how for_each_child_of_node() is ridiculously hard to use
correct.
Regards,
Hans
---
drivers/ata/libahci_platform.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/ata/libahci_platform.c b/drivers/ata/libahci_platform.c
index 9e9583a6bba9..e742780950de 100644
--- a/drivers/ata/libahci_platform.c
+++ b/drivers/ata/libahci_platform.c
@@ -497,6 +497,7 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
if (of_property_read_u32(child, "reg", &port)) {
rc = -EINVAL;
+ of_node_put(child);
goto err_out;
}
@@ -514,14 +515,18 @@ struct ahci_host_priv *ahci_platform_get_resources(struct platform_device *pdev,
if (port_dev) {
rc = ahci_platform_get_regulator(hpriv, port,
&port_dev->dev);
- if (rc == -EPROBE_DEFER)
+ if (rc == -EPROBE_DEFER) {
+ of_node_put(child);
goto err_out;
+ }
}
#endif
rc = ahci_platform_get_phy(hpriv, port, dev, child);
- if (rc)
+ if (rc) {
+ of_node_put(child);
goto err_out;
+ }
enabled_ports++;
}
