[PATCH 5.7 050/265] net: dsa: bcm_sf2: Fix node reference count

Sasha Levin
2020-06-29T21:53:57Z

From: Florian Fainelli <f.fainelli@gmail.com>

[ Upstream commit 8dbe4c5d5e40fe140221024f7b16bec9f310bf70 ]

of_find_node_by_name() will do an of_node_put() on the "from" argument.
With CONFIG_OF_DYNAMIC enabled which checks for device_node reference
counts, we would be getting a warning like this:

[ 6.347230] refcount_t: increment on 0; use-after-free.
[ 6.352498] WARNING: CPU: 3 PID: 77 at lib/refcount.c:156
refcount_inc_checked+0x38/0x44
[ 6.360601] Modules linked in:
[ 6.363661] CPU: 3 PID: 77 Comm: kworker/3:1 Tainted: G W
5.4.46-gb78b3e9956e6 #13
[ 6.372546] Hardware name: BCM97278SV (DT)
[ 6.376649] Workqueue: events deferred_probe_work_func
[ 6.381796] pstate: 60000005 (nZCv daif -PAN -UAO)
[ 6.386595] pc : refcount_inc_checked+0x38/0x44
[ 6.391133] lr : refcount_inc_checked+0x38/0x44
...
[ 6.478791] Call trace:
[ 6.481243] refcount_inc_checked+0x38/0x44
[ 6.485433] kobject_get+0x3c/0x4c
[ 6.488840] of_node_get+0x24/0x34
[ 6.492247] of_irq_find_parent+0x3c/0xe0
[ 6.496263] of_irq_parse_one+0xe4/0x1d0
[ 6.500191] irq_of_parse_and_map+0x44/0x84
[ 6.504381] bcm_sf2_sw_probe+0x22c/0x844
[ 6.508397] platform_drv_probe+0x58/0xa8
[ 6.512413] really_probe+0x238/0x3fc
[ 6.516081] driver_probe_device+0x11c/0x12c
[ 6.520358] __device_attach_driver+0xa8/0x100
[ 6.524808] bus_for_each_drv+0xb4/0xd0
[ 6.528650] __device_attach+0xd0/0x164
[ 6.532493] device_initial_probe+0x24/0x30
[ 6.536682] bus_probe_device+0x38/0x98
[ 6.540524] deferred_probe_work_func+0xa8/0xd4
[ 6.545061] process_one_work+0x178/0x288
[ 6.549078] process_scheduled_works+0x44/0x48
[ 6.553529] worker_thread+0x218/0x270
[ 6.557285] kthread+0xdc/0xe4
[ 6.560344] ret_from_fork+0x10/0x18
[ 6.563925] ---[ end trace 68f65caf69bb152a ]---

Fix this by adding a of_node_get() to increment the reference count
prior to the call.

Fixes: afa3b592953b ("net: dsa: bcm_sf2: Ensure correct sub-node is parsed")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/dsa/bcm_sf2.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
index c7ac63f419184..946e41f020a56 100644
--- a/drivers/net/dsa/bcm_sf2.c
+++ b/drivers/net/dsa/bcm_sf2.c
@@ -1147,6 +1147,8 @@ static int bcm_sf2_sw_probe(struct platform_device *pdev)
set_bit(0, priv->cfp.used);
set_bit(0, priv->cfp.unique);

+ /* Balance of_node_put() done by of_find_node_by_name() */
+ of_node_get(dn);
ports = of_find_node_by_name(dn, "ports");
if (ports) {
bcm_sf2_identify_ports(priv, ports);
--
2.25.1