Messages in this thread | | | Date | Wed, 2 Nov 2022 12:08:00 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] hamradio: baycom_epp: Fix return type of baycom_send_packet() |
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On Wed, Nov 02, 2022 at 09:06:10AM -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 > proposed warning in clang aims to catch these at compile time, which > reveals: > > drivers/net/hamradio/baycom_epp.c:1119:25: 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 = baycom_send_packet, > ^~~~~~~~~~~~~~~~~~ > 1 error generated. > > ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of > 'netdev_tx_t', not 'int'. Adjust the return type of baycom_send_packet() > to match the prototype's to resolve the warning and CFI failure. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1750 > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Heh, this one was already using the enum for the argument to "return", too. :)
Reviewed-by: Kees Cook <keescook@chromium.org>
-- Kees Cook
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