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/lcs.c:2090:21: 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 = lcs_start_xmit, > ^~~~~~~~~~~~~~ > drivers/s390/net/lcs.c:2097:21: 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 = lcs_start_xmit, > ^~~~~~~~~~~~~~ > > ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of > 'netdev_tx_t', not 'int'. Adjust the return type of lcs_start_xmit() 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/lcs.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c > index 84c8981317b4..4cbb9802bf22 100644 > --- a/drivers/s390/net/lcs.c > +++ b/drivers/s390/net/lcs.c > @@ -1519,7 +1519,7 @@ lcs_txbuffer_cb(struct lcs_channel *channel, struct lcs_buffer *buffer) > /* > * Packet transmit function called by network stack > */ > -static int > +static netdev_tx_t > __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb, > struct net_device *dev) > { > @@ -1582,7 +1582,7 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb, > return rc; > } > > -static int > +static netdev_tx_t > lcs_start_xmit(struct sk_buff *skb, struct net_device *dev) > { > struct lcs_card *card; Thanks a lot for the fix. Could you please also fix the indentation of these lines? With that: Reviewed-by: Alexandra Winter <wintera@xxxxxxxxxxxxx>
