Commit f262f5d8 authored May 20, 2026 by Wei Fang Committed by Jakub Kicinski May 21, 2026

net: enetc: fix race condition in VF MAC address configuration

Sashiko reported a potential race condition between the VF message
handler and administrative VF MAC configuration from the host [1].

The VF message handler (enetc_msg_pf_set_vf_primary_mac_addr) runs
asynchronously in a workqueue context and accesses vf_state->flags
without any locking. Concurrently, the host can administratively
change the VF MAC address via enetc_pf_set_vf_mac(), which executes
under RTNL lock and modifies both vf_state->flags and hardware
registers.

This creates two race windows:

1) TOCTOU race on vf_state->flags: The check of ENETC_VF_FLAG_PF_SET_MAC
   and subsequent MAC programming are not atomic, allowing the flag state
   to change between check and use.

2) Torn MAC address writes: Hardware MAC programming requires multiple
   non-atomic register writes (__raw_writel for lower 32 bits and
   __raw_writew for upper 16 bits). Concurrent updates from VF mailbox
   and PF admin paths can interleave these operations, resulting in a
   corrupted MAC address being programmed into the hardware.

Fix by introducing a per-VF mutex to serialize access to vf_state and
hardware MAC register updates. Both enetc_pf_set_vf_mac() and
enetc_msg_pf_set_vf_primary_mac_addr() now acquire this lock before
accessing vf_state->flags or programming the MAC address, ensuring
atomic read-modify-write sequences and preventing register write
interleaving.

Link: https://sashiko.dev/#/patchset/20260511080805.2052495-1-wei.fang%40nxp.com

 #1
Fixes: beb74ac8 ("enetc: Add vf to pf messaging support")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20260520064421.91569-6-wei.fang@nxp.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent c666fa63

drivers/net/ethernet/freescale/enetc/enetc_pf.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -252,8 +252,12 @@ static int enetc_pf_set_vf_mac(struct net_device ndev, int vf, u8 mac)
		return -EADDRNOTAVAIL;

		vf_state = &pf->vf_state[vf];

		mutex_lock(&vf_state->lock);
		vf_state->flags \|= ENETC_VF_FLAG_PF_SET_MAC;
		enetc_pf_set_primary_mac_addr(&priv->si->hw, vf + 1, mac);
		mutex_unlock(&vf_state->lock);

		return 0;
		}

		@@ -496,7 +500,9 @@ static u16 enetc_msg_pf_set_vf_primary_mac_addr(struct enetc_pf *pf,
		return ENETC_MSG_CMD_STATUS_FAIL;
		}

		mutex_lock(&vf_state->lock);
		if (vf_state->flags & ENETC_VF_FLAG_PF_SET_MAC) {
		mutex_unlock(&vf_state->lock);
		dev_err_ratelimited(dev,
		"VF%d attempted to override PF set MAC\n",
		vf_id);
		@@ -504,6 +510,7 @@ static u16 enetc_msg_pf_set_vf_primary_mac_addr(struct enetc_pf *pf,
		}

		enetc_pf_set_primary_mac_addr(&pf->si->hw, vf_id + 1, addr);
		mutex_unlock(&vf_state->lock);

		return ENETC_MSG_CMD_STATUS_OK;
		}
		@@ -989,6 +996,9 @@ static int enetc_pf_probe(struct pci_dev *pdev,
		err = -ENOMEM;
		goto err_alloc_vf_state;
		}

		for (int i = 0; i < pf->total_vfs; i++)
		mutex_init(&pf->vf_state[i].lock);
		}

		err = enetc_setup_mac_addresses(node, pf);

drivers/net/ethernet/freescale/enetc/enetc_pf.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -14,6 +14,7 @@ enum enetc_vf_flags {
		};

		struct enetc_vf_state {
		struct mutex lock; /* Prevent concurrent access */
		enum enetc_vf_flags flags;
		};