Commit 8b3fae3e authored by Meghana Malladi's avatar Meghana Malladi Committed by Jakub Kicinski
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net: ti: icssg-prueth: Fix kernel panic during concurrent Tx queue access 

Add __netif_tx_lock() to ensure that only one packet is being
transmitted at a time to avoid race conditions in the netif_txq
struct and prevent packet data corruption. Failing to do so causes
kernel panic with the following error:

[ 2184.746764] ------------[ cut here ]------------
[ 2184.751412] kernel BUG at lib/dynamic_queue_limits.c:99!
[ 2184.756728] Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP

logs: https://gist.github.com/MeghanaMalladiTI/9c7aa5fc3b7fb03f87c74aad487956e9



The lock is acquired before calling emac_xmit_xdp_frame() and released after the
call returns. This ensures that the TX queue is protected from concurrent access
during the transmission of XDP frames.

Fixes: 62aa3246 ("net: ti: icssg-prueth: Add XDP support")
Signed-off-by: default avatarMeghana Malladi <m-malladi@ti.com>
Reviewed-by: default avatarJacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250506110546.4065715-3-m-malladi@ti.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent e5641daa

drivers/net/ethernet/ti/icssg/icssg_common.c

+6 −1
Original line number Diff line number Diff line
@@ -650,6 +650,8 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, 
			struct page *page, u32 *len)

{

	struct net_device *ndev = emac->ndev;

	struct netdev_queue *netif_txq;

	int cpu = smp_processor_id();

	struct bpf_prog *xdp_prog;

	struct xdp_frame *xdpf;

	u32 pkt_len = *len;
@@ -669,8 +671,11 @@ static u32 emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp, 
			goto drop;

		}



		q_idx = smp_processor_id() % emac->tx_ch_num;

		q_idx = cpu % emac->tx_ch_num;

		netif_txq = netdev_get_tx_queue(ndev, q_idx);

		__netif_tx_lock(netif_txq, cpu);

		result = emac_xmit_xdp_frame(emac, xdpf, page, q_idx);

		__netif_tx_unlock(netif_txq);

		if (result == ICSSG_XDP_CONSUMED) {

			ndev->stats.tx_dropped++;

			goto drop;

drivers/net/ethernet/ti/icssg/icssg_prueth.c

+6 −1
Original line number Diff line number Diff line
@@ -1075,17 +1075,21 @@ static int emac_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frame 
{

	struct prueth_emac *emac = netdev_priv(dev);

	struct net_device *ndev = emac->ndev;

	struct netdev_queue *netif_txq;

	int cpu = smp_processor_id();

	struct xdp_frame *xdpf;

	unsigned int q_idx;

	int nxmit = 0;

	u32 err;

	int i;



	q_idx = smp_processor_id() % emac->tx_ch_num;

	q_idx = cpu % emac->tx_ch_num;

	netif_txq = netdev_get_tx_queue(ndev, q_idx);



	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))

		return -EINVAL;



	__netif_tx_lock(netif_txq, cpu);

	for (i = 0; i < n; i++) {

		xdpf = frames[i];

		err = emac_xmit_xdp_frame(emac, xdpf, NULL, q_idx);
@@ -1095,6 +1099,7 @@ static int emac_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frame 
		}

		nxmit++;

	}

	__netif_tx_unlock(netif_txq);



	return nxmit;

}