From b345f330aeed0edbaf3ace089886bcbed030528f Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 6 Dec 2023 09:49:46 -0700 Subject: um: net: Fix return type of uml_net_start_xmit() [ Upstream commit 7d748f60a4b82b50bf25fad1bd42d33f049f76aa ] 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 warning in clang aims to catch these at compile time, which reveals: arch/um/drivers/net_kern.c:353:21: warning: 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 *)' [-Wincompatible-function-pointer-types-strict] 353 | .ndo_start_xmit = uml_net_start_xmit, | ^~~~~~~~~~~~~~~~~~ 1 warning generated. ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of 'netdev_tx_t', not 'int'. Adjust the return type of uml_net_start_xmit() to match the prototype's to resolve the warning. While UML does not currently implement support for kCFI, it could in the future, which means this warning becomes a fatal CFI failure at run time. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202310031340.v1vPh207-lkp@intel.com/ Acked-by: Anton Ivanov Signed-off-by: Nathan Chancellor Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin --- arch/um/drivers/net_kern.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch') diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c index 1802cf4ef5a5..ee55333255d0 100644 --- a/arch/um/drivers/net_kern.c +++ b/arch/um/drivers/net_kern.c @@ -204,7 +204,7 @@ static int uml_net_close(struct net_device *dev) return 0; } -static int uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev) +static netdev_tx_t uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct uml_net_private *lp = netdev_priv(dev); unsigned long flags; -- cgit v1.2.3