Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH AUTOSEL 5.12 13/63] net: caif: remove BUG_ON(dev == NULL) in caif_xmit | Date | Mon, 24 May 2021 10:45:30 -0400 |
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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.org 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 4720a7bac4fb..9f30748da4ab 100644 --- a/drivers/net/caif/caif_serial.c +++ b/drivers/net/caif/caif_serial.c @@ -269,7 +269,6 @@ static netdev_tx_t 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
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