Re: ROX allocations broke livepatch for modules since 6.13-rc1

[Petr Pavlu <petr.pavlu@suse.com>]

On 1/5/25 15:51, Petr Pavlu wrote:
> On 12/30/24 01:09, Marek Maślanka wrote:
>> Hi Mike and others,
>>
>> I discovered that the patch "[v7,4/8] module: prepare to handle ROX allocations
>> for text" has disrupted livepatch functionality. Specifically, this occurs when
>> livepatch is prepared to patch a kernel module and when the livepatch module
>> contains a "special" relocation section named
>> ".klp.rela.<MODULE_NAME>.<SECTION_NAME>" to access local symbols.
> 
> Thank you for the report. It is possible for me to reproduce the issue
> on my system. An annoying part is to create the
> .klp.rela.<objname>.<secname> data, for which I eventually used one
> floating variant of klp-convert [1]. To hit the problem, <objname> must
> point to an object that is different from vmlinux. Such relocations are
> processed by the livepatch code later than regular module relocations,
> as you pointed out after mod->rw_copy is already reset.
> 
> I think the bug should be addressed in principle by Mike's recently
> posted rework of the feature [2] but unfortunately, its current version
> makes my system also unbootable [3].

A simpler fix could be:

diff --git a/include/linux/module.h b/include/linux/module.h
index 94acbacdcdf1..b3a643435357 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -773,7 +773,8 @@ void *__module_writable_address(struct module *mod, void *loc);
 
 static inline void *module_writable_address(struct module *mod, void *loc)
 {
-	if (!IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX) || !mod)
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX) || !mod ||
+	    mod->state != MODULE_STATE_UNFORMED)
 		return loc;
 	return __module_writable_address(mod, loc);
 }

Hm, is it expected that Mike's rework to drop rw_copy will make it into
6.13 or should I properly post this minimal fix for review?

-- 
Thanks,
Petr