Hello. Thanks for this submission. Please see one comment inline. On středa 20. dubna 2022 13:52:57 CEST Aaron Tomlin wrote: > Currently, only the initial module that tainted the kernel is > recorded e.g. when an out-of-tree module is loaded. > > The purpose of this patch is to allow the kernel to maintain a record of > each unloaded module that taints the kernel. So, in addition to > displaying a list of linked modules (see print_modules()) e.g. in the > event of a detected bad page, unloaded modules that carried a taint/or > taints are displayed too. A tainted module unload count is maintained. > > The number of tracked modules is not fixed. This feature is disabled by > default. > > Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx> > --- > init/Kconfig | 11 ++++++++ > kernel/module/main.c | 65 ++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 76 insertions(+) > > diff --git a/init/Kconfig b/init/Kconfig > index ddcbefe535e9..6b30210f787d 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -2118,6 +2118,17 @@ config MODULE_FORCE_UNLOAD > rmmod). This is mainly for kernel developers and desperate users. > If unsure, say N. > > +config MODULE_UNLOAD_TAINT_TRACKING > + bool "Tainted module unload tracking" > + depends on MODULE_UNLOAD > + default n > + help > + This option allows you to maintain a record of each unloaded > + module that tainted the kernel. In addition to displaying a > + list of linked (or loaded) modules e.g. on detection of a bad > + page (see bad_page()), the aforementioned details are also > + shown. If unsure, say N. > + > config MODVERSIONS > bool "Module versioning support" > help > diff --git a/kernel/module/main.c b/kernel/module/main.c > index ea78cec316dd..d7cc64172dd1 100644 > --- a/kernel/module/main.c > +++ b/kernel/module/main.c > @@ -68,6 +68,16 @@ > */ > DEFINE_MUTEX(module_mutex); > LIST_HEAD(modules); > +#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING > +static LIST_HEAD(unloaded_tainted_modules); > + > +struct mod_unload_taint { > + struct list_head list; > + char name[MODULE_NAME_LEN]; > + unsigned long taints; > + u64 count; > +}; > +#endif > > /* Work queue for freeing init sections in success case */ > static void do_free_init(struct work_struct *w); > @@ -150,6 +160,41 @@ int unregister_module_notifier(struct notifier_block *nb) > } > EXPORT_SYMBOL(unregister_module_notifier); > > +#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING > +static int try_add_tainted_module(struct module *mod) > +{ > + struct mod_unload_taint *mod_taint; > + > + module_assert_mutex_or_preempt(); > + > + list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules, list, > + lockdep_is_held(&module_mutex)) { > + size_t len = strlen(mod_taint->name); > + > + if (len == strlen(mod->name) && !memcmp(mod_taint->name, mod->name, len) && Here, two strings are compared, so I'd expect to see `strncmp()` instead of `memcmp()`. > + mod_taint->taints & mod->taints) { > + mod_taint->count++; > + goto out; > + } > + } > + > + mod_taint = kmalloc(sizeof(*mod_taint), GFP_KERNEL); > + if (unlikely(!mod_taint)) > + return -ENOMEM; > + strscpy(mod_taint->name, mod->name, MODULE_NAME_LEN); > + mod_taint->taints = mod->taints; > + list_add_rcu(&mod_taint->list, &unloaded_tainted_modules); > + mod_taint->count = 1; > +out: > + return 0; > +} > +#else /* MODULE_UNLOAD_TAINT_TRACKING */ > +static int try_add_tainted_module(struct module *mod) > +{ > + return 0; > +} > +#endif > + > /* > * We require a truly strong try_module_get(): 0 means success. > * Otherwise an error is returned due to ongoing or failed > @@ -1201,6 +1246,9 @@ static void free_module(struct module *mod) > module_bug_cleanup(mod); > /* Wait for RCU-sched synchronizing before releasing mod->list and buglist. */ > synchronize_rcu(); > + if (try_add_tainted_module(mod)) > + pr_err("%s: adding tainted module to the unloaded tainted modules list failed.\n", > + mod->name); > mutex_unlock(&module_mutex); > > /* Clean up CFI for the module. */ > @@ -3126,6 +3174,9 @@ struct module *__module_text_address(unsigned long addr) > void print_modules(void) > { > struct module *mod; > +#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING > + struct mod_unload_taint *mod_taint; > +#endif > char buf[MODULE_FLAGS_BUF_SIZE]; > > printk(KERN_DEFAULT "Modules linked in:"); > @@ -3136,6 +3187,20 @@ void print_modules(void) > continue; > pr_cont(" %s%s", mod->name, module_flags(mod, buf)); > } > +#ifdef CONFIG_MODULE_UNLOAD_TAINT_TRACKING > + if (!list_empty(&unloaded_tainted_modules)) { > + printk(KERN_DEFAULT "Unloaded tainted modules:"); > + list_for_each_entry_rcu(mod_taint, &unloaded_tainted_modules, > + list) { > + size_t l; > + > + l = module_flags_taint(mod_taint->taints, buf); > + buf[l++] = '\0'; > + pr_cont(" %s(%s):%llu", mod_taint->name, buf, > + mod_taint->count); > + } > +#endif > + } > preempt_enable(); > if (last_unloaded_module[0]) > pr_cont(" [last unloaded: %s]", last_unloaded_module); > -- Oleksandr Natalenko (post-factum)