netdev - [PATCH net v2] net: stmmac: Complete meta data only when enabled

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Message-Id: <20240222-stmmac_xdp-v2-1-4beee3a037e4@linutronix.de>
Date: Sun, 25 Feb 2024 12:38:37 +0100
From: Kurt Kanzenbach <kurt@...utronix.de>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>, 
 Jose Abreu <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 Song Yoong Siang <yoong.siang.song@...el.com>, 
 Stanislav Fomichev <sdf@...gle.com>, 
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>, 
 Serge Semin <fancer.lancer@...il.com>, 
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, netdev@...r.kernel.org, 
 linux-stm32@...md-mailman.stormreply.com, 
 linux-arm-kernel@...ts.infradead.org, bpf@...r.kernel.org, 
 Kurt Kanzenbach <kurt@...utronix.de>
Subject: [PATCH net v2] net: stmmac: Complete meta data only when enabled

Currently using plain XDP/ZC sockets on stmmac results in a kernel crash:

|[  255.822584] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
|[...]
|[  255.822764] Call trace:
|[  255.822766]  stmmac_tx_clean.constprop.0+0x848/0xc38

The program counter indicates xsk_tx_metadata_complete(). It works on
compl->tx_timestamp, which is not set by xsk_tx_metadata_to_compl() due to
missing meta data. Therefore, call xsk_tx_metadata_complete() only when
meta data is actually used.

Tested on imx93 without XDP, with XDP and with XDP/ZC.

Fixes: 1347b419318d ("net: stmmac: Add Tx HWTS support to XDP ZC")
Suggested-by: Serge Semin <fancer.lancer@...il.com>
Tested-by: Serge Semin <fancer.lancer@...il.com>
Link: https://lore.kernel.org/netdev/87r0h7wg8u.fsf@kurt.kurt.home/
Acked-by: Stanislav Fomichev <sdf@...gle.com>
Signed-off-by: Kurt Kanzenbach <kurt@...utronix.de>
---
Changes in v2:
- Add more details to change log (Maciej)
- Link to v1: https://lore.kernel.org/r/20240222-stmmac_xdp-v1-1-e8d2d2b79ff0@linutronix.de
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index e80d77bd9f1f..8b77c0952071 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2672,7 +2672,8 @@ static int stmmac_tx_clean(struct stmmac_priv *priv, int budget, u32 queue,
 			}
 			if (skb) {
 				stmmac_get_tx_hwtstamp(priv, p, skb);
-			} else {
+			} else if (tx_q->xsk_pool &&
+				   xp_tx_metadata_enabled(tx_q->xsk_pool)) {
 				struct stmmac_xsk_tx_complete tx_compl = {
 					.priv = priv,
 					.desc = p,

---
base-commit: 2a770cdc4382b457ca3d43d03f0f0064f905a0d0
change-id: 20240222-stmmac_xdp-585ebf1680b3

Best regards,
-- 
Kurt Kanzenbach <kurt@...utronix.de>