On Wed, Nov 02, 2022 at 09:19:06AM -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/scsi/elx/libefc/efc_node.c:811:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
> ctx->current_state = state;
> ^ ~~~~~
> drivers/scsi/elx/libefc/efc_node.c:878:21: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
> node->nodedb_state = state;
> ^ ~~~~~
> drivers/scsi/elx/libefc/efc_node.c:905:6: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' from 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') [-Werror,-Wincompatible-function-pointer-types-strict]
> pf = node->nodedb_state;
> ^ ~~~~~~~~~~~~~~~~~~
>
> drivers/scsi/elx/libefc/efc_device.c:455:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
> node->nodedb_state = __efc_d_init;
> ^ ~~~~~~~~~~~~
>
> drivers/scsi/elx/libefc/efc_sm.c:41:22: error: incompatible function pointer types assigning to 'void (*)(struct efc_sm_ctx *, u32, void *)' (aka 'void (*)(struct efc_sm_ctx *, unsigned int, void *)') from 'void (*)(struct efc_sm_ctx *, enum efc_sm_event, void *)' [-Werror,-Wincompatible-function-pointer-types-strict]
> ctx->current_state = state;
> ^ ~~~~~
>
> The type of the second parameter in the prototypes of ->current_state()
> and ->nodedb_state() ('u32') does not match the implementations, which
> have a second parameter type of 'enum efc_sm_event'. Update the
> prototypes to have the correct second parameter type, clearing up all
> the warnings and CFI failures.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Reported-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
--
Kees Cook
