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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org (open list) Subject: [PATCH net] net: gianfar: handle startup_gfar failure and fix double free Date: Fri, 28 Aug 2026 15:20:51 -0700 Message-ID: <20260828222051.77604-1-rosenp@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit reset_gfar() ignores the return value of startup_gfar(), so a reset that fails to reallocate resources (e.g. -ENOMEM) leaves the interface logically UP with stale descriptor-ring pointers. If the device is closed afterwards, gfar_close() -> stop_gfar() -> free_skb_resources() frees the same coherent DMA ring a second time, causing a double free of the TX/RX buffer descriptors. Make reset_gfar() and gfar_change_mtu() propagate the startup_gfar() error instead of silently continuing. Make free_skb_resources() idempotent by NULLing the descriptor-ring base pointers after freeing them, so a second free cannot operate on a stale pointer regardless of which error path is taken. Fixes: 0851133bb5ad ("gianfar: Fix device reset races (oops) for Tx") Assisted-by: opencode:big-pickle Signed-off-by: Rosen Penev --- drivers/net/ethernet/freescale/gianfar.c | 42 +++++++++++++++++------- 1 file changed, 30 insertions(+), 12 deletions(-) diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index cf636fc5aafa..d0ac8a958696 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -1140,11 +1140,24 @@ static void free_skb_resources(struct gfar_private *priv) free_skb_rx_queue(rx_queue); } - dma_free_coherent(priv->dev, - sizeof(struct txbd8) * priv->total_tx_ring_size + - sizeof(struct rxbd8) * priv->total_rx_ring_size, - priv->tx_queue[0]->tx_bd_base, - priv->tx_queue[0]->tx_bd_dma_base); + if (priv->tx_queue[0]->tx_bd_base) { + dma_free_coherent(priv->dev, + sizeof(struct txbd8) * + priv->total_tx_ring_size + + sizeof(struct rxbd8) * + priv->total_rx_ring_size, + priv->tx_queue[0]->tx_bd_base, + priv->tx_queue[0]->tx_bd_dma_base); + + for (i = 0; i < priv->num_tx_queues; i++) { + priv->tx_queue[i]->tx_bd_base = NULL; + priv->tx_queue[i]->tx_bd_dma_base = 0; + } + for (i = 0; i < priv->num_rx_queues; i++) { + priv->rx_queue[i]->rx_bd_base = NULL; + priv->rx_queue[i]->rx_bd_dma_base = 0; + } + } } void stop_gfar(struct net_device *dev) @@ -2003,6 +2016,7 @@ static int gfar_set_mac_address(struct net_device *dev) static int gfar_change_mtu(struct net_device *dev, int new_mtu) { struct gfar_private *priv = netdev_priv(dev); + int err = 0; while (test_and_set_bit_lock(GFAR_RESETTING, &priv->state)) cpu_relax(); @@ -2013,24 +2027,27 @@ static int gfar_change_mtu(struct net_device *dev, int new_mtu) WRITE_ONCE(dev->mtu, new_mtu); if (dev->flags & IFF_UP) - startup_gfar(dev); + err = startup_gfar(dev); clear_bit_unlock(GFAR_RESETTING, &priv->state); - return 0; + return err; } -static void reset_gfar(struct net_device *ndev) +static int reset_gfar(struct net_device *ndev) { struct gfar_private *priv = netdev_priv(ndev); + int ret; while (test_and_set_bit_lock(GFAR_RESETTING, &priv->state)) cpu_relax(); stop_gfar(ndev); - startup_gfar(ndev); + ret = startup_gfar(ndev); clear_bit_unlock(GFAR_RESETTING, &priv->state); + + return ret; } /* gfar_reset_task gets scheduled when a packet has not been @@ -2058,6 +2075,7 @@ static int gfar_hwtstamp_set(struct net_device *netdev, struct netlink_ext_ack *extack) { struct gfar_private *priv = netdev_priv(netdev); + int ret = 0; switch (config->tx_type) { case HWTSTAMP_TX_OFF: @@ -2076,7 +2094,7 @@ static int gfar_hwtstamp_set(struct net_device *netdev, case HWTSTAMP_FILTER_NONE: if (priv->hwts_rx_en) { priv->hwts_rx_en = 0; - reset_gfar(netdev); + ret = reset_gfar(netdev); } break; default: @@ -2084,13 +2102,13 @@ static int gfar_hwtstamp_set(struct net_device *netdev, return -ERANGE; if (!priv->hwts_rx_en) { priv->hwts_rx_en = 1; - reset_gfar(netdev); + ret = reset_gfar(netdev); } config->rx_filter = HWTSTAMP_FILTER_ALL; break; } - return 0; + return ret; } static int gfar_hwtstamp_get(struct net_device *netdev, -- 2.55.0