On 11/12/24 10:43, Daniel Gomez wrote: > On Mon Nov 11, 2024 at 7:53 PM CET, Christophe Leroy wrote: >> >> >> Le 09/11/2024 à 23:17, Daniel Gomez a écrit : >>> On Sat Nov 9, 2024 at 11:35 AM CET, Christophe Leroy wrote: >>>> Once module init has succeded it is too late to cancel loading. >>>> If setting ro_after_init data section to read-only fails, all we >>>> can do is to inform the user through a warning. >>>> >>>> Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> >>>> Closes: https://protect2.fireeye.com/v1/url?k=d3deb284-b2a35ac3-d3df39cb-74fe485fff30-288375d7d91e4ad9&q=1&e=701066ca-634d-4525-a77d-1a44451f897a&u=https%3A%2F%2Feur01.safelinks.protection.outlook.com%2F%3Furl%3Dhttps%253A%252F%252Flore.kernel.org%252Fall%252F20230915082126.4187913-1-ruanjinjie%2540huawei.com%252F%26data%3D05%257C02%257Cchristophe.leroy%2540csgroup.eu%257C26b5ca7363e54210439b08dd010c4865%257C8b87af7d86474dc78df45f69a2011bb5%257C0%257C0%257C638667874457200373%257CUnknown%257CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%253D%253D%257C0%257C%257C%257C%26sdata%3DZeJ%252F3%252B2Nx%252FBf%252FWLFEkhxKlDhZk8LNkz0fs%252Fg2xMcOjY%253D%26reserved%3D0 >>>> Fixes: d1909c022173 ("module: Don't ignore errors from set_memory_XX()") >>>> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx> >>>> --- >>>> kernel/module/main.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/kernel/module/main.c b/kernel/module/main.c >>>> index 2de4ad7af335..1bf4b0db291b 100644 >>>> --- a/kernel/module/main.c >>>> +++ b/kernel/module/main.c >>>> @@ -2583,7 +2583,9 @@ static noinline int do_init_module(struct module *mod) >>>> #endif >>>> ret = module_enable_rodata_ro_after_init(mod); >>>> if (ret) >>>> - goto fail_mutex_unlock; >>>> + pr_warn("%s: %s() returned %d, ro_after_init data might still be writable\n", >>>> + mod->name, __func__, ret); >>>> + >>>> mod_tree_remove_init(mod); >>>> module_arch_freeing_init(mod); >>>> for_class_mod_mem_type(type, init) { >>>> @@ -2622,8 +2624,6 @@ static noinline int do_init_module(struct module *mod) >>>> >>>> return 0; >>> >>> I think it would make sense to propagate the error. But that would >>> require changing modprobe.c. What kind of error can we expect when this >>> happens? >> >> AFAIK, on powerpc it fails with EINVAL when >> - The area is a vmalloc or module area and is a hugepage area >> - The area is not vmalloc or io register and MMU is not powerpc radix MMU >> >> Otherwise it propagates the error from apply_to_existing_page_range(). >> IIUC it will return EINVAL when it hits a leaf PTE in upper directories. > > Looking at that path I see we can also fail at __apply_to_page_range() > -> apply_to_p4d_range() and return with -ENOMEM. > > My proposal was to do something like the change below in modprobe: > > diff --git a/tools/modprobe.c b/tools/modprobe.c > index ec66e6f..8876e27 100644 > --- a/tools/modprobe.c > +++ b/tools/modprobe.c > @@ -572,6 +572,11 @@ static int insmod_insert(struct kmod_module *mod, int flags, const char *extra_o > err = 0; > else { > switch (err) { > + case -EINVAL: > + ERR("module '%s'inserted: ro_after_init data might" > + "still be writable (see dmesg)\n", > + kmod_module_get_name(mod)); > + break; > case -EEXIST: > ERR("could not insert '%s': Module already in kernel\n", > kmod_module_get_name(mod)); > > But I think these error codes may be also be reported in other parts > such as simplify_symbols() so may not be a good idea after all. It isn't really possible to make a sensible use of the return code from init_module(), besides some basic check for -EEXIST. The problem is that any error code from a module's init function is also propagated as a result from the syscall. > > Maybe we just need to change the default/catch all error message in > modprobe.c and to indicate/include this case: > > diff --git a/tools/modprobe.c b/tools/modprobe.c > index ec66e6f..3647d37 100644 > --- a/tools/modprobe.c > +++ b/tools/modprobe.c > @@ -582,7 +582,8 @@ static int insmod_insert(struct kmod_module *mod, int flags, const char *extra_o > kmod_module_get_name(mod)); > break; > default: > - ERR("could not insert '%s': %s\n", kmod_module_get_name(mod), > + ERR("could not insert '%s' or inserted with error %s, " > + "(see dmesg)\n", kmod_module_get_name(mod), > strerror(-err)); > break; > } > > >> >> On other architectures it can be different, I know some architecture try >> to split the pages when they hit hugepages and that can fail. > > Is it worth it adding an error code for this case in case we want to > report it back? I feel that the proposed kernel warning about this situation is sufficient and the loader should then return 0 to indicate that the module got loaded. It would be more confusing to return an error but with the module actually remaining inserted. A module loaded without having its RO-after-init section changed properly to RO is still fully functional. In practice, if this final set_memory_ro() call fails, the system is already in such a state where the additional warning is the least of the issues? -- Thanks, Petr
