[PATCH net 2/2] net: mana: Skip redundant detach in queue reset handler if already detached

[Dipayaan Roy <dipayanroy@linux.microsoft.com>]

When mana_per_port_queue_reset_work_handler() runs, it unconditionally
calls mana_detach() which attempts to tear down queues that are already
freed, leading to NULL pointer dereferences on apc->tx_qp and
apc->rxqs.

Check netif_device_present() in the reset handler and skip
mana_detach() when the port is already in detached state. This avoids
the redundant teardown and goes directly to mana_attach() to retry
bringing the port back up.

Fixes: 3b194343c250 ("net: mana: Implement ndo_tx_timeout and serialize queue resets per port.")
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Dipayaan Roy <dipayanroy@linux.microsoft.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 0582803907a8..907efadf6fd6 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -316,12 +316,19 @@ static void mana_per_port_queue_reset_work_handler(struct work_struct *work)
 		goto out;
 	}
 
+	/* If already detached (indicates detach succeeded but attach failed
+	 * previously). Now skip mana detach and just retry mana_attach.
+	 */
+	if (!netif_device_present(ndev))
+		goto attach;
+
 	err = mana_detach(ndev, false);
 	if (err) {
 		netdev_err(ndev, "mana_detach failed: %d\n", err);
 		goto dealloc_pre_rxbufs;
 	}
 
+attach:
 	err = mana_attach(ndev);
 	if (err)
 		netdev_err(ndev, "mana_attach failed: %d\n", err);
-- 
2.43.0