net: ethernet: mtk_eth_soc: Reset prog ptr to old_prog in case of error in mtk_xdp_setup()

[ Upstream commit 0abc73c ]

Reset eBPF program pointer to old_prog and do not decrease its ref-count
if mtk_open routine in mtk_xdp_setup() fails.

Fixes: 7c26c20 ("net: ethernet: mtk_eth_soc: add basic XDP support")
Suggested-by: Paolo Valerio <pvalerio@redhat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260303-mtk-xdp-prog-ptr-fix-v2-1-97b6dbbe240f@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: LorenzoBianconi

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -3749,12 +3749,21 @@ static int mtk_xdp_setup(struct net_device *dev, struct bpf_prog *prog,
 		mtk_stop(dev);
 
 	old_prog = rcu_replace_pointer(eth->prog, prog, lockdep_rtnl_is_held());
+
+	if (netif_running(dev) && need_update) {
+		int err;
+
+		err = mtk_open(dev);
+		if (err) {
+			rcu_assign_pointer(eth->prog, old_prog);
+
+			return err;
+		}
+	}
+
 	if (old_prog)
 		bpf_prog_put(old_prog);
 
-	if (netif_running(dev) && need_update)
-		return mtk_open(dev);
-
 	return 0;
 }