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Subject[PATCH net-next v2] net: phy: Fix suspicious rcu_dereference usage
Date
The phy_detach function can be called with or without the rtnl lock held.
When the rtnl lock is not held, using rtnl_dereference() triggers a
warning due to the lack of lock context.

Add an rcu_read_lock() to ensure the lock is acquired and to maintain
synchronization.

Tested-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Reported-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Closes: https://lore.kernel.org/netdev/4c6419d8-c06b-495c-b987-d66c2e1ff848@tuxon.dev/
Fixes: 35f7cad1743e ("net: Add the possibility to support a selected hwtstamp in netdevice")
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
---

Changes in v2:
- Add a missing ;
---
drivers/net/phy/phy_device.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 5b34d39d1d52..3eeee7cba923 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -2001,12 +2001,14 @@ void phy_detach(struct phy_device *phydev)
if (dev) {
struct hwtstamp_provider *hwprov;

- hwprov = rtnl_dereference(dev->hwprov);
+ rcu_read_lock();
+ hwprov = rcu_dereference(dev->hwprov);
/* Disable timestamp if it is the one selected */
if (hwprov && hwprov->phydev == phydev) {
rcu_assign_pointer(dev->hwprov, NULL);
kfree_rcu(hwprov, rcu_head);
}
+ rcu_read_unlock();

phydev->attached_dev->phydev = NULL;
phydev->attached_dev = NULL;
--
2.34.1

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