From: Nathan Chancellor nathan@kernel.org
[ Upstream commit 88d86d18d7cf7e9137c95f9d212bb9fff8a1b4be ]
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.
Additionally, while in the area, remove a comment block that is no longer relevant.
Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Reviewed-by: Alexandra Winter wintera@linux.ibm.com Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/net/netiucv.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/drivers/s390/net/netiucv.c b/drivers/s390/net/netiucv.c index 5ce2424ca729..e2984b54447b 100644 --- a/drivers/s390/net/netiucv.c +++ b/drivers/s390/net/netiucv.c @@ -1344,15 +1344,8 @@ static int netiucv_pm_restore_thaw(struct 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) +static netdev_tx_t netiucv_tx(struct sk_buff *skb, struct net_device *dev) { struct netiucv_priv *privptr = netdev_priv(dev); int rc;