(2014/04/22 12:51), Rusty Russell wrote: > Steven Rostedt <rost...@goodmis.org> writes: >> On Mon, 24 Mar 2014 20:26:05 +0900 >> Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote: >> >> >>> Thank you for reporting with this pretty backtrace :) >>> Steven, I think this is not the kprobe bug but ftrace (and perhaps, module). >> >> Looks to be more of a module issue than a ftrace issue. >> >>> >>> If the ftrace can set loading module text read only before the module >>> subsystem >>> expected, I think it should be protected by the module subsystem itself >>> (e.g. set_all_modules_text_ro(rw) skips the modules which is >>> MODULE_STATE_COMING) >>> >> >> Does this patch fix it? >> >> In-review-off-by: Steven Rostedt <rost...@goodmis.org> > > Sorry, was on paternity leave. > > I'm always nervous about adding more states, since every place which > examines the state has to be audited. > > We set the mod->state to MOD_STATE_COMING in complete_formation; > why don't we set NX there instead? It also makes more sense to > set NX before we hit parse_args() which can execute code in the module. > > In fact, we should probably call the notifier there too, so people > can breakpoint/tracepoint/etc parameter calls. > > Of course, this means that we set NX before the notifier; does anything > break?
This does not work. ftrace_process_locs() is called from the notifier, and it tries to change its text like this. load_module blocking_notifier_call_chain ftrace_module_notify_enter ftrace_init_module ftrace_process_locs sort ftrace_swap_ips But the text is already RO, so it causes panic. We need to call notifier before setting it RO. Or should we unset RO temporarily in ftrace_process_locs()? Thanks, Takao Indoh > > Subject: module: set nx before marking module MODULE_STATE_COMING. > > This prevents a WARN_ON() where ftrace calls set_all_modules_text_ro() > which races with the module setting its own set_section_ro_nx(). > > It also means we're NX protected before we call parse_args(), which > can execute module code. > > This means that the notifiers will be called on a module which > is already NX, so that may cause problems. > > Signed-off-by: Rusty Russell <ru...@rustcorp.com.au> > > diff --git a/kernel/module.c b/kernel/module.c > index 11869408f79b..83a437e5d429 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -3023,21 +3023,6 @@ static int do_init_module(struct module *mod) > */ > current->flags &= ~PF_USED_ASYNC; > > - blocking_notifier_call_chain(&module_notify_list, > - MODULE_STATE_COMING, mod); > - > - /* Set RO and NX regions for core */ > - set_section_ro_nx(mod->module_core, > - mod->core_text_size, > - mod->core_ro_size, > - mod->core_size); > - > - /* Set RO and NX regions for init */ > - set_section_ro_nx(mod->module_init, > - mod->init_text_size, > - mod->init_ro_size, > - mod->init_size); > - > do_mod_ctors(mod); > /* Start the module */ > if (mod->init != NULL) > @@ -3168,9 +3153,26 @@ static int complete_formation(struct module *mod, > struct load_info *info) > /* This relies on module_mutex for list integrity. */ > module_bug_finalize(info->hdr, info->sechdrs, mod); > > + /* Set RO and NX regions for core */ > + set_section_ro_nx(mod->module_core, > + mod->core_text_size, > + mod->core_ro_size, > + mod->core_size); > + > + /* Set RO and NX regions for init */ > + set_section_ro_nx(mod->module_init, > + mod->init_text_size, > + mod->init_ro_size, > + mod->init_size); > + > /* Mark state as coming so strong_try_module_get() ignores us, > * but kallsyms etc. can see us. */ > mod->state = MODULE_STATE_COMING; > + mutex_unlock(&module_mutex); > + > + blocking_notifier_call_chain(&module_notify_list, > + MODULE_STATE_COMING, mod); > + return 0; > > out: > mutex_unlock(&module_mutex); > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/