Merge tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull module and param fixes from Rusty Russell:
 "Surprising number of fixes this merge window :(

  The first two are minor fallout from the param rework which went in
  this merge window.

  The next three are a series which fixes a longstanding (but never
  previously reported and unlikely , so no CC stable) race between
  kallsyms and freeing the init section.

  Finally, a minor cleanup as our module refcount will now be -1 during
  unload"

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux:
  module: make module_refcount() a signed integer.
  module: fix race in kallsyms resolution during module load success.
  module: remove mod arg from module_free, rename module_memfree().
  module_arch_freeing_init(): new hook for archs before module->module_init freed.
  param: fix uninitialized read with CONFIG_DEBUG_LOCK_ALLOC
  param: initialize store function to NULL if not available.

5 files changed, 74 insertions, 26 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index d6594e457a25..a64e7a207d2b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -163,7 +163,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
 
 void bpf_jit_binary_free(struct bpf_binary_header *hdr)
 {
-        module_free(NULL, hdr);
+        module_memfree(hdr);
 }
 #endif /* CONFIG_BPF_JIT */
 
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index f191bddf64b8..7b40c5f07dce 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2023,7 +2023,7 @@ static int kdb_lsmod(int argc, const char **argv)
                 kdb_printf("%-20s%8u  0x%p ", mod->name,
                            mod->core_size, (void *)mod);
 #ifdef CONFIG_MODULE_UNLOAD
-                kdb_printf("%4ld ", module_refcount(mod));
+                kdb_printf("%4d ", module_refcount(mod));
 #endif
                 if (mod->state == MODULE_STATE_GOING)
                         kdb_printf(" (Unloading)");
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 06f58309fed2..ee619929cf90 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -127,7 +127,7 @@ static void *alloc_insn_page(void)
 
 static void free_insn_page(void *page)
 {
-        module_free(NULL, page);
+        module_memfree(page);
 }
 
 struct kprobe_insn_cache kprobe_insn_slots = {
diff --git a/kernel/module.c b/kernel/module.c
index 3965511ae133..d856e96a3cce 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -772,9 +772,18 @@ static int try_stop_module(struct module *mod, int flags, int *forced)
         return 0;
 }
 
-unsigned long module_refcount(struct module *mod)
+/**
+ * module_refcount - return the refcount or -1 if unloading
+ *
+ * @mod:        the module we're checking
+ *
+ * Returns:
+ *      -1 if the module is in the process of unloading
+ *      otherwise the number of references in the kernel to the module
+ */
+int module_refcount(struct module *mod)
 {
-        return (unsigned long)atomic_read(&mod->refcnt) - MODULE_REF_BASE;
+        return atomic_read(&mod->refcnt) - MODULE_REF_BASE;
 }
 EXPORT_SYMBOL(module_refcount);
 
@@ -856,7 +865,7 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
         struct module_use *use;
         int printed_something = 0;
 
-        seq_printf(m, " %lu ", module_refcount(mod));
+        seq_printf(m, " %i ", module_refcount(mod));
 
         /*
          * Always include a trailing , so userspace can differentiate
@@ -908,7 +917,7 @@ EXPORT_SYMBOL_GPL(symbol_put_addr);
 static ssize_t show_refcnt(struct module_attribute *mattr,
                            struct module_kobject *mk, char *buffer)
 {
-        return sprintf(buffer, "%lu\n", module_refcount(mk->mod));
+        return sprintf(buffer, "%i\n", module_refcount(mk->mod));
 }
 
 static struct module_attribute modinfo_refcnt =
@@ -1795,7 +1804,7 @@ static void unset_module_core_ro_nx(struct module *mod) { }
 static void unset_module_init_ro_nx(struct module *mod) { }
 #endif
 
-void __weak module_free(struct module *mod, void *module_region)
+void __weak module_memfree(void *module_region)
 {
         vfree(module_region);
 }
@@ -1804,6 +1813,10 @@ void __weak module_arch_cleanup(struct module *mod)
 {
 }
 
+void __weak module_arch_freeing_init(struct module *mod)
+{
+}
+
 /* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
@@ -1841,7 +1854,8 @@ static void free_module(struct module *mod)
 
         /* This may be NULL, but that's OK */
         unset_module_init_ro_nx(mod);
-        module_free(mod, mod->module_init);
+        module_arch_freeing_init(mod);
+        module_memfree(mod->module_init);
         kfree(mod->args);
         percpu_modfree(mod);
 
@@ -1850,7 +1864,7 @@ static void free_module(struct module *mod)
 
         /* Finally, free the core (containing the module structure) */
         unset_module_core_ro_nx(mod);
-        module_free(mod, mod->module_core);
+        module_memfree(mod->module_core);
 
 #ifdef CONFIG_MPU
         update_protections(current->mm);
@@ -2785,7 +2799,7 @@ static int move_module(struct module *mod, struct load_info *info)
                  */
                 kmemleak_ignore(ptr);
                 if (!ptr) {
-                        module_free(mod, mod->module_core);
+                        module_memfree(mod->module_core);
                         return -ENOMEM;
                 }
                 memset(ptr, 0, mod->init_size);
@@ -2930,8 +2944,9 @@ static struct module *layout_and_allocate(struct load_info *info, int flags)
 static void module_deallocate(struct module *mod, struct load_info *info)
 {
         percpu_modfree(mod);
-        module_free(mod, mod->module_init);
-        module_free(mod, mod->module_core);
+        module_arch_freeing_init(mod);
+        module_memfree(mod->module_init);
+        module_memfree(mod->module_core);
 }
 
 int __weak module_finalize(const Elf_Ehdr *hdr,
@@ -2983,10 +2998,31 @@ static void do_mod_ctors(struct module *mod)
 #endif
 }
 
+/* For freeing module_init on success, in case kallsyms traversing */
+struct mod_initfree {
+        struct rcu_head rcu;
+        void *module_init;
+};
+
+static void do_free_init(struct rcu_head *head)
+{
+        struct mod_initfree *m = container_of(head, struct mod_initfree, rcu);
+        module_memfree(m->module_init);
+        kfree(m);
+}
+
 /* This is where the real work happens */
 static int do_init_module(struct module *mod)
 {
         int ret = 0;
+        struct mod_initfree *freeinit;
+
+        freeinit = kmalloc(sizeof(*freeinit), GFP_KERNEL);
+        if (!freeinit) {
+                ret = -ENOMEM;
+                goto fail;
+        }
+        freeinit->module_init = mod->module_init;
 
         /*
          * We want to find out whether @mod uses async during init.  Clear
@@ -2999,18 +3035,7 @@ static int do_init_module(struct module *mod)
         if (mod->init != NULL)
                 ret = do_one_initcall(mod->init);
         if (ret < 0) {
-                /*
-                 * Init routine failed: abort.  Try to protect us from
-                 * buggy refcounters.
-                 */
-                mod->state = MODULE_STATE_GOING;
-                synchronize_sched();
-                module_put(mod);
-                blocking_notifier_call_chain(&module_notify_list,
-                                             MODULE_STATE_GOING, mod);
-                free_module(mod);
-                wake_up_all(&module_wq);
-                return ret;
+                goto fail_free_freeinit;
         }
         if (ret > 0) {
                 pr_warn("%s: '%s'->init suspiciously returned %d, it should "
@@ -3055,15 +3080,35 @@ static int do_init_module(struct module *mod)
         mod->strtab = mod->core_strtab;
 #endif
         unset_module_init_ro_nx(mod);
-        module_free(mod, mod->module_init);
+        module_arch_freeing_init(mod);
         mod->module_init = NULL;
         mod->init_size = 0;
         mod->init_ro_size = 0;
         mod->init_text_size = 0;
+        /*
+         * We want to free module_init, but be aware that kallsyms may be
+         * walking this with preempt disabled.  In all the failure paths,
+         * we call synchronize_rcu/synchronize_sched, but we don't want
+         * to slow down the success path, so use actual RCU here.
+         */
+        call_rcu(&freeinit->rcu, do_free_init);
         mutex_unlock(&module_mutex);
         wake_up_all(&module_wq);
 
         return 0;
+
+fail_free_freeinit:
+        kfree(freeinit);
+fail:
+        /* Try to protect us from buggy refcounters. */
+        mod->state = MODULE_STATE_GOING;
+        synchronize_sched();
+        module_put(mod);
+        blocking_notifier_call_chain(&module_notify_list,
+                                     MODULE_STATE_GOING, mod);
+        free_module(mod);
+        wake_up_all(&module_wq);
+        return ret;
 }
 
 static int may_init_module(void)
diff --git a/kernel/params.c b/kernel/params.c
index 0af9b2c4e56c..728e05b167de 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -642,12 +642,15 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
         mk->mp->grp.attrs = new_attrs;
 
         /* Tack new one on the end. */
+        memset(&mk->mp->attrs[mk->mp->num], 0, sizeof(mk->mp->attrs[0]));
         sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
         mk->mp->attrs[mk->mp->num].param = kp;
         mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
         /* Do not allow runtime DAC changes to make param writable. */
         if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
                 mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
+        else
+                mk->mp->attrs[mk->mp->num].mattr.store = NULL;
         mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
         mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
         mk->mp->num++;