[PATCH AUTOSEL 4.19 04/25] net: caif: remove BUG_ON(dev == NULL) in caif_xmit
From: Sasha Levin <sashal@kernel.org>
Date: 2021-05-24 15:10:25
Also in:
lkml, netdev
Subsystem:
networking drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Du Cheng <redacted> [ 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 <redacted> Link: https://lore.kernel.org/r/20210503115736.2104747-20-gregkh@linuxfoundation.org (local) 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 a0f954f36c09..94d5ce9419ca 100644
--- a/drivers/net/caif/caif_serial.c
+++ b/drivers/net/caif/caif_serial.c@@ -279,7 +279,6 @@ 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 */
--
2.30.2