Re: [PATCH] mei: late_bind: Fix -Wincompatible-function-pointer-types-strict

[Nathan Chancellor <nathan@kernel.org>]

On Thu, Oct 23, 2025 at 09:27:03AM -0500, Lucas De Marchi wrote:
> On Sat, Sep 20, 2025 at 04:17:50PM -0700, Nathan Chancellor wrote:
> > When building with -Wincompatible-function-pointer-types-strict, a
> > warning designed to catch kernel control flow integrity (kCFI) issues at
> > build time, there is an instance in the new mei late binding code
> > originating from the type parameter of mei_lb_push_payload():
> > 
> >  drivers/misc/mei/mei_lb.c:211:18: error: incompatible function pointer types initializing 'int (*)(struct device *, u32, u32, const void *, size_t)' (aka 'int (*)(struct device *, unsigned int, unsigned int, const void *, unsigned long)') with an expression of type 'int (struct device *, enum intel_lb_type, u32, const void *, size_t)' (aka 'int (struct device *, enum intel_lb_type, unsigned int, const void *, unsigned long)') [-Werror,-Wincompatible-function-pointer-types-strict]
> >    211 |         .push_payload = mei_lb_push_payload,
> >        |                         ^~~~~~~~~~~~~~~~~~~
> > 
> > While 'unsigned int' and 'enum intel_lb_type' are ABI compatible, hence
> > no regular warning from -Wincompatible-function-pointer-types, the
> > mismatch will trigger a kCFI violation when mei_lb_push_payload() is
> > called indirectly.
> > 
> > Update the type parameter of mei_lb_push_payload() to be 'u32' to match
> > the prototype in 'struct intel_lb_component_ops', clearing up the
> > warning and kCFI violation.
> > 
> > Fixes: 741eeabb7c78 ("mei: late_bind: add late binding component driver")
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> 
> Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
> 
> Sasha, is this fix something you are taking through char-misc since the
> commits that added it already propagated through the 6.18-rc?

It looks like Greg already took this via char-misc-linus:

https://git.kernel.org/gregkh/char-misc/c/98718e80af0bb1cd80f4bfe565dd60c57debad51

Cheers,
Nathan