On Wed, Nov 02, 2022 at 08:25:40AM -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/gpu/drm/amd/amdgpu/../pm/swsmu/amdgpu_smu.c:3008:29: error: incompatible function pointer types initializing 'int (*)(void *, uint32_t, long *, uint32_t)' (aka 'int (*)(void *, unsigned int, long *, unsigned int)') with an expression of type 'int (void *, enum PP_OD_DPM_TABLE_COMMAND, long *, uint32_t)' (aka 'int (void *, enum PP_OD_DPM_TABLE_COMMAND, long *, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict] > .odn_edit_dpm_table = smu_od_edit_dpm_table, > ^~~~~~~~~~~~~~~~~~~~~ > 1 error generated. > > There are only two implementations of ->odn_edit_dpm_table() in 'struct > amd_pm_funcs': smu_od_edit_dpm_table() and pp_odn_edit_dpm_table(). One > has a second parameter type of 'enum PP_OD_DPM_TABLE_COMMAND' and the > other uses 'u32'. Ultimately, smu_od_edit_dpm_table() calls > ->od_edit_dpm_table() from 'struct pptable_funcs' and > pp_odn_edit_dpm_table() calls ->odn_edit_dpm_table() from 'struct > pp_hwmgr_func', which both have a second parameter type of 'enum > PP_OD_DPM_TABLE_COMMAND'. > > Update the type parameter in both the prototype in 'struct amd_pm_funcs' > and pp_odn_edit_dpm_table() to 'enum PP_OD_DPM_TABLE_COMMAND', which > cleans up the warning. > > 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
