On 02.11.22 17:32, Nathan Chancellor wrote: > With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), > indirect call targets are validated against the expected function > pointer prototype to make sure the call target is valid to help mitigate > ROP attacks. If they are not identical, there is a failure at run time, > which manifests as either a kernel panic or thread getting killed. A > proposed warning in clang aims to catch these at compile time, which > reveals: > > drivers/s390/net/netiucv.c:1854:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict] > .ndo_start_xmit = netiucv_tx, > ^~~~~~~~~~ > > ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of > 'netdev_tx_t', not 'int'. Adjust the return type of netiucv_tx() to > match the prototype's to resolve the warning and potential CFI failure, > should s390 select ARCH_SUPPORTS_CFI_CLANG in the future. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1750 > Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx> > --- > drivers/s390/net/netiucv.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c > index 65aa0a96c21d..1a7f2bc3a87b 100644 > --- a/drivers/s390/net/netiucv.c > +++ b/drivers/s390/net/netiucv.c > @@ -1256,7 +1256,7 @@ static int netiucv_close(struct net_device *dev) > * Note: If we return !0, then the packet is free'd by > * the generic network layer. > */ > -static int netiucv_tx(struct sk_buff *skb, struct net_device *dev) > +static netdev_tx_t netiucv_tx(struct sk_buff *skb, struct net_device *dev) > { > struct netiucv_priv *privptr = netdev_priv(dev); > int rc; Could you please also remove the corresponding comments: diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c index 65aa0a96c21d..21e36f63fbc7 100644 --- a/drivers/s390/net/netiucv.c +++ b/drivers/s390/net/netiucv.c @@ -1248,13 +1248,6 @@ static int netiucv_close(struct net_device *dev) /* * Start transmission of a packet. * Called from generic network device layer. - * - * @param skb Pointer to buffer containing the packet. - * @param dev Pointer to interface struct. - * - * @return 0 if packet consumed, !0 if packet rejected. - * Note: If we return !0, then the packet is free'd by - * the generic network layer. */ static int netiucv_tx(struct sk_buff *skb, struct net_device *dev) { Reviewed-by: Alexandra Winter <wintera@xxxxxxxxxxxxx>
