Re: [PATCH] MODSIGN: only panic in fips mode if sig_enforce is set

[Rusty Russell <rusty@rustcorp.com.au>]

Kyle McMartin <kyle@redhat.com> writes:
> Commit 1d0059f3a added a test to check if the system is booted in fips
> mode, and if so, panic the system if an unsigned module is loaded.
> However the wording of the changelog "in signature enforcing mode" leads
> one to assume that sig_enforce should be set for the panic to occur and
> that these two tests are transposed.
>
> Move the test for -ENOKEY && !sig_enforce before the test of fips_mode,
> so that err will be 0, and the panic will not trigger unless we've
> explicitly disabled unsigned modules with sig_enforce set, so that
> systemtap and 3rd party modules will work in fips mode. (This also
> matches the behaviour by Red Hat Enterprise Linux 6.)
>
> Things which need to deny module loading such as secure boot already set
> sig_enforce, so there's no issue here.
>
> Reported-by: Jan Stancek <jstancek@redhat.com>
> Signed-off-by: Kyle McMartin <kyle@redhat.com>

Seems reasonable, but I'll want David Howells' Ack.

Thanks,
Rusty.

> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2460,11 +2460,11 @@ static int module_sig_check(struct load_info *info)
>  	}
>  
>  	/* Not having a signature is only an error if we're strict. */
> +	if (err == -ENOKEY && !sig_enforce)
> +		err = 0;
>  	if (err < 0 && fips_enabled)
>  		panic("Module verification failed with error %d in FIPS mode\n",
>  		      err);
> -	if (err == -ENOKEY && !sig_enforce)
> -		err = 0;
>  
>  	return err;
>  }