[PATCH net v2 1/2] net: ravb: Fix missing rtnl lock in suspend path

[Kory Maincent <kory.maincent@bootlin.com>]

Fix the suspend path by ensuring the rtnl lock is held where required.
Calls to ravb_open, ravb_close and wol operations must be performed under
the rtnl lock to prevent conflicts with ongoing ndo operations.

Without this fix, the following warning is triggered:
[   39.032969] =============================
[   39.032983] WARNING: suspicious RCU usage
[   39.033019] -----------------------------
[   39.033033] drivers/net/phy/phy_device.c:2004 suspicious
rcu_dereference_protected() usage!
...
[   39.033597] stack backtrace:
[   39.033613] CPU: 0 UID: 0 PID: 174 Comm: python3 Not tainted
6.13.0-rc7-next-20250116-arm64-renesas-00002-g35245dfdc62c #7
[   39.033623] Hardware name: Renesas SMARC EVK version 2 based on
r9a08g045s33 (DT)
[   39.033628] Call trace:
[   39.033633]  show_stack+0x14/0x1c (C)
[   39.033652]  dump_stack_lvl+0xb4/0xc4
[   39.033664]  dump_stack+0x14/0x1c
[   39.033671]  lockdep_rcu_suspicious+0x16c/0x22c
[   39.033682]  phy_detach+0x160/0x190
[   39.033694]  phy_disconnect+0x40/0x54
[   39.033703]  ravb_close+0x6c/0x1cc
[   39.033714]  ravb_suspend+0x48/0x120
[   39.033721]  dpm_run_callback+0x4c/0x14c
[   39.033731]  device_suspend+0x11c/0x4dc
[   39.033740]  dpm_suspend+0xdc/0x214
[   39.033748]  dpm_suspend_start+0x48/0x60
[   39.033758]  suspend_devices_and_enter+0x124/0x574
[   39.033769]  pm_suspend+0x1ac/0x274
[   39.033778]  state_store+0x88/0x124
[   39.033788]  kobj_attr_store+0x14/0x24
[   39.033798]  sysfs_kf_write+0x48/0x6c
[   39.033808]  kernfs_fop_write_iter+0x118/0x1a8
[   39.033817]  vfs_write+0x27c/0x378
[   39.033825]  ksys_write+0x64/0xf4
[   39.033833]  __arm64_sys_write+0x18/0x20
[   39.033841]  invoke_syscall+0x44/0x104
[   39.033852]  el0_svc_common.constprop.0+0xb4/0xd4
[   39.033862]  do_el0_svc+0x18/0x20
[   39.033870]  el0_svc+0x3c/0xf0
[   39.033880]  el0t_64_sync_handler+0xc0/0xc4
[   39.033888]  el0t_64_sync+0x154/0x158
[   39.041274] ravb 11c30000.ethernet eth0: Link is Down

Reported-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Closes: https://lore.kernel.org/netdev/4c6419d8-c06b-495c-b987-d66c2e1ff848@tuxon.dev/
Fixes: 0184165b2f42 ("ravb: add sleep PM suspend/resume support")
Reviewed-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
---

Changes in v2:
- Move the rtnl_lock before ravb_wol_setup() and and ravb_wol_restore()
  instead of before the if condition.
---
 drivers/net/ethernet/renesas/ravb_main.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index bc395294a32d..cfe4f0f364f3 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -3217,10 +3217,16 @@ static int ravb_suspend(struct device *dev)
 
 	netif_device_detach(ndev);
 
-	if (priv->wol_enabled)
-		return ravb_wol_setup(ndev);
+	if (priv->wol_enabled) {
+		rtnl_lock();
+		ret = ravb_wol_setup(ndev);
+		rtnl_unlock();
+		return ret;
+	}
 
+	rtnl_lock();
 	ret = ravb_close(ndev);
+	rtnl_unlock();
 	if (ret)
 		return ret;
 
@@ -3247,7 +3253,9 @@ static int ravb_resume(struct device *dev)
 
 	/* If WoL is enabled restore the interface. */
 	if (priv->wol_enabled) {
+		rtnl_lock();
 		ret = ravb_wol_restore(ndev);
+		rtnl_unlock();
 		if (ret)
 			return ret;
 	} else {
@@ -3257,7 +3265,9 @@ static int ravb_resume(struct device *dev)
 	}
 
 	/* Reopening the interface will restore the device to the working state. */
+	rtnl_lock();
 	ret = ravb_open(ndev);
+	rtnl_unlock();
 	if (ret < 0)
 		goto out_rpm_put;
 

-- 
2.34.1