On Wed, Dec 06, 2023 at 07:19:35AM +0000, Anton Ivanov wrote: > > > On 05/12/2023 17:53, Nathan Chancellor wrote: > > Ping? I would like to turn this warning on for W=1 and the kbuild test > > robot flagged this instance. If the UML folks don't want to carry it, > > could I get an ack so that it could go with the warning enablement in > > the kbuild tree? > > > > https://lore.kernel.org/20231002-enable-wincompatible-function-pointer-types-strict-w-1-v1-1-808ab955d...@kernel.org/ > > > > On Tue, Oct 03, 2023 at 11:35:53AM -0700, 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 > > > 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 <l...@intel.com> > > > Closes: > > > https://lore.kernel.org/oe-kbuild-all/202310031340.v1vph207-...@intel.com/ > > > Signed-off-by: Nathan Chancellor <nat...@kernel.org> > > > --- > > > arch/um/drivers/net_kern.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c > > > index 3d7836c46507..cabcc501b448 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; > > > > > > --- > > > base-commit: 8a749fd1a8720d4619c91c8b6e7528c0a355c0aa > > > change-id: 20231003-um-net-wifpts-14a7429c7524 > > > > > > Best regards, > > > -- > > > Nathan Chancellor <nat...@kernel.org> > > > > > > > > > Looks ok to me. > Acked-By: Anton Ivanov <anton.iva...@cambridgegreys.com>
Thanks a lot, I have included this change in v2 of the series to turn this warning on for W=1, so Masahiro should be able to carry it: https://lore.kernel.org/20231206-enable-wincompatible-function-pointer-types-strict-w-1-v2-1-91311b4c3...@kernel.org Cheers, Nathan
