Surprising number of fixes this merge window :(

First two are minor fallout from the param rework which went in this merge
 window.
 
 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.
 
 Thanks,
 Rusty.
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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.

arch/avr32/kernel/module.c

@@ -19,12 +19,10 @@
 #include <linux/moduleloader.h>
 #include <linux/vmalloc.h>
 
-void module_free(struct module *mod, void *module_region)
+void module_arch_freeing_init(struct module *mod)
 {
 	vfree(mod->arch.syminfo);
 	mod->arch.syminfo = NULL;
-
-	vfree(module_region);
 }
 
 static inline int check_rela(Elf32_Rela *rela, struct module *module,
@@ -291,12 +289,3 @@ int apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab,
 
 	return ret;
 }
-
-int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
-		    struct module *module)
-{
-	vfree(module->arch.syminfo);
-	module->arch.syminfo = NULL;
-
-	return 0;
-}

arch/cris/kernel/module.c

@@ -36,7 +36,7 @@ void *module_alloc(unsigned long size)
 }
 
 /* Free memory returned from module_alloc */
-void module_free(struct module *mod, void *module_region)
+void module_memfree(void *module_region)
 {
 	kfree(module_region);
 }

arch/ia64/kernel/module.c

@@ -305,14 +305,12 @@ plt_target (struct plt_entry *plt)
 #endif /* !USE_BRL */
 
 void
-module_free (struct module *mod, void *module_region)
+module_arch_freeing_init (struct module *mod)
 {
-	if (mod && mod->arch.init_unw_table &&
+	if (mod->arch.init_unw_table) {
-	    module_region == mod->module_init) {
 		unw_remove_unwind_table(mod->arch.init_unw_table);
 		mod->arch.init_unw_table = NULL;
 	}
-	vfree(module_region);
 }
 
 /* Have we already seen one of these relocations? */

arch/mips/net/bpf_jit.c

@@ -1388,7 +1388,7 @@ out:
 void bpf_jit_free(struct bpf_prog *fp)
 {
 	if (fp->jited)
-		module_free(NULL, fp->bpf_func);
+		module_memfree(fp->bpf_func);
 
 	bpf_prog_unlock_free(fp);
 }

arch/nios2/kernel/module.c

@@ -36,7 +36,7 @@ void *module_alloc(unsigned long size)
 }
 
 /* Free memory returned from module_alloc */
-void module_free(struct module *mod, void *module_region)
+void module_memfree(void *module_region)
 {
 	kfree(module_region);
 }

arch/parisc/kernel/module.c

@@ -298,14 +298,10 @@ static inline unsigned long count_stubs(const Elf_Rela *rela, unsigned long n)
 }
 #endif
 
-
+void module_arch_freeing_init(struct module *mod)
-/* Free memory returned from module_alloc */
-void module_free(struct module *mod, void *module_region)
 {
 	kfree(mod->arch.section);
 	mod->arch.section = NULL;
-
-	vfree(module_region);
 }
 
 /* Additional bytes needed in front of individual sections */

arch/powerpc/net/bpf_jit_comp.c

@@ -699,7 +699,7 @@ out:
 void bpf_jit_free(struct bpf_prog *fp)
 {
 	if (fp->jited)
-		module_free(NULL, fp->bpf_func);
+		module_memfree(fp->bpf_func);
 
 	bpf_prog_unlock_free(fp);
 }

arch/s390/kernel/module.c

@@ -55,14 +55,10 @@ void *module_alloc(unsigned long size)
 }
 #endif
 
-/* Free memory returned from module_alloc */
+void module_arch_freeing_init(struct module *mod)
-void module_free(struct module *mod, void *module_region)
 {
-	if (mod) {
+	vfree(mod->arch.syminfo);
-		vfree(mod->arch.syminfo);
+	mod->arch.syminfo = NULL;
-		mod->arch.syminfo = NULL;
-	}
-	vfree(module_region);
 }
 
 static void check_rela(Elf_Rela *rela, struct module *me)

arch/sparc/net/bpf_jit_comp.c

@@ -776,7 +776,7 @@ cond_branch:			f_offset = addrs[i + filter[i].jf];
 				if (unlikely(proglen + ilen > oldproglen)) {
 					pr_err("bpb_jit_compile fatal error\n");
 					kfree(addrs);
-					module_free(NULL, image);
+					module_memfree(image);
 					return;
 				}
 				memcpy(image + proglen, temp, ilen);
@@ -822,7 +822,7 @@ out:
 void bpf_jit_free(struct bpf_prog *fp)
 {
 	if (fp->jited)
-		module_free(NULL, fp->bpf_func);
+		module_memfree(fp->bpf_func);
 
 	bpf_prog_unlock_free(fp);
 }

arch/tile/kernel/module.c

@@ -74,7 +74,7 @@ error:
 
 
 /* Free memory returned from module_alloc */
-void module_free(struct module *mod, void *module_region)
+void module_memfree(void *module_region)
 {
 	vfree(module_region);
 
@@ -83,7 +83,7 @@ void module_free(struct module *mod, void *module_region)
 		     0, 0, 0, NULL, NULL, 0);
 
 	/*
-	 * FIXME: If module_region == mod->module_init, trim exception
+	 * FIXME: Add module_arch_freeing_init to trim exception
 	 * table entries.
 	 */
 }

arch/x86/kernel/ftrace.c

@@ -674,7 +674,7 @@ static inline void *alloc_tramp(unsigned long size)
 }
 static inline void tramp_free(void *tramp)
 {
-	module_free(NULL, tramp);
+	module_memfree(tramp);
 }
 #else
 /* Trampolines can only be created if modules are supported */

include/linux/module.h

@@ -444,7 +444,7 @@ extern void __module_put_and_exit(struct module *mod, long code)
 #define module_put_and_exit(code) __module_put_and_exit(THIS_MODULE, code)
 
 #ifdef CONFIG_MODULE_UNLOAD
-unsigned long module_refcount(struct module *mod);
+int module_refcount(struct module *mod);
 void __symbol_put(const char *symbol);
 #define symbol_put(x) __symbol_put(VMLINUX_SYMBOL_STR(x))
 void symbol_put_addr(void *addr);

include/linux/moduleloader.h

@@ -26,7 +26,7 @@ unsigned int arch_mod_section_prepend(struct module *mod, unsigned int section);
 void *module_alloc(unsigned long size);
 
 /* Free memory returned from module_alloc. */
-void module_free(struct module *mod, void *module_region);
+void module_memfree(void *module_region);
 
 /*
  * Apply the given relocation to the (simplified) ELF.  Return -error
@@ -82,4 +82,6 @@ int module_finalize(const Elf_Ehdr *hdr,
 /* Any cleanup needed when module leaves. */
 void module_arch_cleanup(struct module *mod);
 
+/* Any cleanup before freeing mod->module_init */
+void module_arch_freeing_init(struct module *mod);
 #endif

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 */
 

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)");

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 = {

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_arch_freeing_init(mod);
-	module_free(mod, mod->module_core);
+	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) {
-		/*
+		goto fail_free_freeinit;
-		 * 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;
 	}
 	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)

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++;