On Fri Nov 8, 2024 at 4:49 PM CET, Luis Chamberlain wrote: > + Other new module maintainers > > On Fri, Nov 08, 2024 at 09:12:03AM +0100, Christophe Leroy wrote: >> Hi Luis, >> >> Le 24/09/2024 à 09:22, Mike Rapoport a écrit : >> > On Thu, Sep 19, 2024 at 02:53:34AM -0700, Luis Chamberlain wrote: >> > > On Fri, Sep 06, 2024 at 04:24:56PM -0700, Luis Chamberlain wrote: >> > > > On Thu, Sep 05, 2024 at 11:44:00AM +0200, Thomas Gleixner wrote: >> > > > > Now you at least provided the information that the missing cleanup in >> > > > > the init() function is not the problem. So the obvious place to look is >> > > > > in the module core code whether there is a failure path _after_ >> > > > > module->init() returned success. >> > > > > >> > > > > do_init_module() >> > > > > ret = do_one_initcall(mod->init); >> > > > > ... >> > > > > ret = module_enable_rodata_ro(mod, true); >> > > > > if (ret) >> > > > > goto fail_mutex_unlock; >> > > > > >> > > > > and that error path does _not_ invoke module->exit(), which is obviously >> > > > > not correct. Luis? >> > > > >> > > > You're spot on this needs fixing. >> > > >> > > Christophe, this is a regression caused by the second hunk of your commit >> > > d1909c0221739 ("module: Don't ignore errors from set_memory_XX()") on v6.9. >> > > Sadly there are a few issues with trying to get to call mod->exit(): >> > > >> > > - We should try try_stop_module() and that can fail >> > > - source_list may not be empty and that would block removal >> > > - mod->exit may not exist >> > > >> > > I'm wondering if instead we should try to do the module_enable_rodata_ro() >> > > before the init, but that requires a bit more careful evaluation... >> > >> > There is ro_after_init section, we can't really make it RO before ->init() >> >> Surprisingly I never received Luis's email > > So odd.. > >> allthough I got this answer from Mike that I overlooked. >> >> So coming back here from >> https://lore.kernel.org/all/ZyQhbHxDTRXTJgIx@xxxxxxxxxxxxxxxxxxxxxx/ >> >> As far as I understand, indeed once init is called it is too late to fail, > > Partly yes, party no. Party yes in that its a can of worms we have not > had to deal with before, and also I worry about deadlocks, and the code > to address this seems complex. right ? I have a RFC ready with this, I'll send this now so we can discuss on with a proposal. > > >> Especially when the module has no exit() path or when >> CONFIG_MODULE_UNLOAD is not built in. > > That's exactly the other extreme case I fear for. > >> So the only thing we can do then is a big fat warning telling >> set_memory_ro() on ro_after_init memory has failed ? > > I suspect this is more sensible to do. I came to the same conclusion while trying to fix this path. + I added an alternative for discussion. > >> Maybe we should try and change it to RO then back to RW before calling init, >> to be on a safer side hopping that if change to RO works once it will work >> twice ? > > That's another approach wich could work, if we proove that this does > work, it's a nice best effort and I think less or a mess to the codebase > then special-casing the error handling of trying to deal with the > driver's exit. > > Daniel Gomez has been looking at this, so his feedback here would be > valuable. What if we detect ro_after_init first, and block any module initialization depending on this ro_after_init to actually start loading it? That way we can stop and unload the module successfully. > > Luis