From: Du Cheng ducheng2@gmail.com
[ Upstream commit 65a67792e3416f7c5d7daa47d99334cbb19a7449 ]
The condition of dev == NULL is impossible in caif_xmit(), hence it is for the removal.
Explanation: The static caif_xmit() is only called upon via a function pointer `ndo_start_xmit` defined in include/linux/netdevice.h: ``` struct net_device_ops { ... netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev); ... } ```
The exhausive list of call points are: ``` drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c dev->netdev_ops->ndo_start_xmit(skb, dev); ^ ^
drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c struct opa_vnic_adapter *adapter = opa_vnic_priv(netdev); ^ ^ return adapter->rn_ops->ndo_start_xmit(skb, netdev); // adapter would crash first ^ ^
drivers/usb/gadget/function/f_ncm.c ncm->netdev->netdev_ops->ndo_start_xmit(NULL, ncm->netdev); ^ ^
include/linux/netdevice.h static inline netdev_tx_t __netdev_start_xmit(... { return ops->ndo_start_xmit(skb, dev); ^ }
const struct net_device_ops *ops = dev->netdev_ops; ^ rc = __netdev_start_xmit(ops, skb, dev, more); ^ ```
In each of the enumerated scenarios, it is impossible for the NULL-valued dev to reach the caif_xmit() without crashing the kernel earlier, therefore `BUG_ON(dev == NULL)` is rather useless, hence the removal.
Cc: David S. Miller davem@davemloft.net Signed-off-by: Du Cheng ducheng2@gmail.com Link: https://lore.kernel.org/r/20210503115736.2104747-20-gregkh@linuxfoundation.o... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/caif/caif_serial.c | 1 - 1 file changed, 1 deletion(-)
diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c index c2dea4916e5d..32834dad0b83 100644 --- a/drivers/net/caif/caif_serial.c +++ b/drivers/net/caif/caif_serial.c @@ -281,7 +281,6 @@ static int caif_xmit(struct sk_buff *skb, struct net_device *dev) { struct ser_device *ser;
- BUG_ON(dev == NULL); ser = netdev_priv(dev);
/* Send flow off once, on high water mark */