modules-5.19-rc7

Although most of the move of code in in v5.19-rc1 should have not
 introduced a regression patch review on one of the file changes captured
 a checkpatch warning which advised to use strscpy() and it caused a
 buffer overflow when an incorrect length is passed.
 
 Another change which checkpatch complained about was an odd RCU usage,
 but that was properly addressed in a separate patch to the move by Aaron.
 That caused a regression with PREEMPT_RT=y due to an unbounded latency.
 
 This series fixes both and adjusts documentation which we forgot to do
 for the move.
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Merge tag 'modules-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

Pull module fixes from Luis Chamberlain:
 "Although most of the move of code in in v5.19-rc1 should have not
  introduced a regression patch review on one of the file changes
  captured a checkpatch warning which advised to use strscpy() and it
  caused a buffer overflow when an incorrect length is passed.

  Another change which checkpatch complained about was an odd RCU usage,
  but that was properly addressed in a separate patch to the move by
  Aaron. That caused a regression with PREEMPT_RT=y due to an unbounded
  latency.

  This series fixes both and adjusts documentation which we forgot to do
  for the move"

* tag 'modules-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux:
  module: kallsyms: Ensure preemption in add_kallsyms() with PREEMPT_RT
  doc: module: update file references
  module: Fix "warning: variable 'exit' set but not used"
  module: Fix selfAssignment cppcheck warning
  modules: Fix corruption of /proc/kallsyms

Documentation/core-api/kernel-api.rst

@@ -223,7 +223,7 @@ Module Loading
 Inter Module support
 --------------------
 
-Refer to the file kernel/module.c for more information.
+Refer to the files in kernel/module/ for more information.
 
 Hardware Interfaces
 ===================

Documentation/core-api/symbol-namespaces.rst

@@ -51,8 +51,8 @@ namespace ``USB_STORAGE``, use::
 The corresponding ksymtab entry struct ``kernel_symbol`` will have the member
 ``namespace`` set accordingly. A symbol that is exported without a namespace will
 refer to ``NULL``. There is no default namespace if none is defined. ``modpost``
-and kernel/module.c make use the namespace at build time or module load time,
-respectively.
+and kernel/module/main.c make use the namespace at build time or module load
+time, respectively.
 
 2.2 Using the DEFAULT_SYMBOL_NAMESPACE define
 =============================================

Documentation/livepatch/module-elf-format.rst

@@ -210,11 +210,11 @@ module->symtab.
 =====================================
 Normally, a stripped down copy of a module's symbol table (containing only
 "core" symbols) is made available through module->symtab (See layout_symtab()
-in kernel/module.c). For livepatch modules, the symbol table copied into memory
-on module load must be exactly the same as the symbol table produced when the
-patch module was compiled. This is because the relocations in each livepatch
-relocation section refer to their respective symbols with their symbol indices,
-and the original symbol indices (and thus the symtab ordering) must be
+in kernel/module/kallsyms.c). For livepatch modules, the symbol table copied
+into memory on module load must be exactly the same as the symbol table produced
+when the patch module was compiled. This is because the relocations in each
+livepatch relocation section refer to their respective symbols with their symbol
+indices, and the original symbol indices (and thus the symtab ordering) must be
 preserved in order for apply_relocate_add() to find the right symbol.
 
 For example, take this particular rela from a livepatch module:::

Documentation/translations/it_IT/core-api/symbol-namespaces.rst

@@ -50,9 +50,9 @@ Di conseguenza, nella tabella dei simboli del kernel ci sarà una voce
 rappresentata dalla struttura ``kernel_symbol`` che avrà il campo
 ``namespace`` (spazio dei nomi) impostato. Un simbolo esportato senza uno spazio
 dei nomi avrà questo campo impostato a ``NULL``. Non esiste uno spazio dei nomi
-di base. Il programma ``modpost`` e il codice in kernel/module.c usano lo spazio
-dei nomi, rispettivamente, durante la compilazione e durante il caricamento
-di un modulo.
+di base. Il programma ``modpost`` e il codice in kernel/module/main.c usano lo
+spazio dei nomi, rispettivamente, durante la compilazione e durante il
+caricamento di un modulo.
 
 2.2 Usare il simbolo di preprocessore DEFAULT_SYMBOL_NAMESPACE
 ==============================================================

Documentation/translations/zh_CN/core-api/kernel-api.rst

@@ -224,7 +224,7 @@ kernel/kmod.c
 模块接口支持
 ------------
 
-更多信息请参考文件kernel/module.c。
+更多信息请参阅kernel/module/目录下的文件。
 
 硬件接口
 ========

Documentation/translations/zh_CN/core-api/symbol-namespaces.rst

@@ -52,7 +52,7 @@
 
 相应的 ksymtab 条目结构体 ``kernel_symbol`` 将有相应的成员 ``命名空间`` 集。
 导出时未指明命名空间的符号将指向 ``NULL`` 。如果没有定义命名空间，则默认没有。
-``modpost`` 和kernel/module.c分别在构建时或模块加载时使用名称空间。
+``modpost`` 和kernel/module/main.c分别在构建时或模块加载时使用名称空间。
 
 2.2 使用DEFAULT_SYMBOL_NAMESPACE定义
 ====================================

kernel/module/internal.h

@@ -11,6 +11,7 @@
 #include <linux/mutex.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
+#include <linux/mm.h>
 
 #ifndef ARCH_SHF_SMALL
 #define ARCH_SHF_SMALL 0
@@ -30,11 +31,13 @@
  * to ensure complete separation of code and data, but
  * only when CONFIG_STRICT_MODULE_RWX=y
  */
-#ifdef CONFIG_STRICT_MODULE_RWX
-# define strict_align(X) PAGE_ALIGN(X)
-#else
-# define strict_align(X) (X)
-#endif
+static inline unsigned int strict_align(unsigned int size)
+{
+	if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
+		return PAGE_ALIGN(size);
+	else
+		return size;
+}
 
 extern struct mutex module_mutex;
 extern struct list_head modules;

kernel/module/kallsyms.c

@@ -137,6 +137,7 @@ void layout_symtab(struct module *mod, struct load_info *info)
 	info->symoffs = ALIGN(mod->data_layout.size, symsect->sh_addralign ?: 1);
 	info->stroffs = mod->data_layout.size = info->symoffs + ndst * sizeof(Elf_Sym);
 	mod->data_layout.size += strtab_size;
+	/* Note add_kallsyms() computes strtab_size as core_typeoffs - stroffs */
 	info->core_typeoffs = mod->data_layout.size;
 	mod->data_layout.size += ndst * sizeof(char);
 	mod->data_layout.size = strict_align(mod->data_layout.size);
@@ -169,19 +170,20 @@ void add_kallsyms(struct module *mod, const struct load_info *info)
 	Elf_Sym *dst;
 	char *s;
 	Elf_Shdr *symsec = &info->sechdrs[info->index.sym];
+	unsigned long strtab_size;
 
 	/* Set up to point into init section. */
 	mod->kallsyms = (void __rcu *)mod->init_layout.base +
 		info->mod_kallsyms_init_off;
 
-	preempt_disable();
+	rcu_read_lock();
 	/* The following is safe since this pointer cannot change */
-	rcu_dereference_sched(mod->kallsyms)->symtab = (void *)symsec->sh_addr;
-	rcu_dereference_sched(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym);
+	rcu_dereference(mod->kallsyms)->symtab = (void *)symsec->sh_addr;
+	rcu_dereference(mod->kallsyms)->num_symtab = symsec->sh_size / sizeof(Elf_Sym);
 	/* Make sure we get permanent strtab: don't use info->strtab. */
-	rcu_dereference_sched(mod->kallsyms)->strtab =
+	rcu_dereference(mod->kallsyms)->strtab =
 		(void *)info->sechdrs[info->index.str].sh_addr;
-	rcu_dereference_sched(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs;
+	rcu_dereference(mod->kallsyms)->typetab = mod->init_layout.base + info->init_typeoffs;
 
 	/*
 	 * Now populate the cut down core kallsyms for after init
@@ -190,22 +192,29 @@ void add_kallsyms(struct module *mod, const struct load_info *info)
 	mod->core_kallsyms.symtab = dst = mod->data_layout.base + info->symoffs;
 	mod->core_kallsyms.strtab = s = mod->data_layout.base + info->stroffs;
 	mod->core_kallsyms.typetab = mod->data_layout.base + info->core_typeoffs;
-	src = rcu_dereference_sched(mod->kallsyms)->symtab;
-	for (ndst = i = 0; i < rcu_dereference_sched(mod->kallsyms)->num_symtab; i++) {
-		rcu_dereference_sched(mod->kallsyms)->typetab[i] = elf_type(src + i, info);
+	strtab_size = info->core_typeoffs - info->stroffs;
+	src = rcu_dereference(mod->kallsyms)->symtab;
+	for (ndst = i = 0; i < rcu_dereference(mod->kallsyms)->num_symtab; i++) {
+		rcu_dereference(mod->kallsyms)->typetab[i] = elf_type(src + i, info);
 		if (i == 0 || is_livepatch_module(mod) ||
 		    is_core_symbol(src + i, info->sechdrs, info->hdr->e_shnum,
 				   info->index.pcpu)) {
+			ssize_t ret;
+
 			mod->core_kallsyms.typetab[ndst] =
-			    rcu_dereference_sched(mod->kallsyms)->typetab[i];
+			    rcu_dereference(mod->kallsyms)->typetab[i];
 			dst[ndst] = src[i];
 			dst[ndst++].st_name = s - mod->core_kallsyms.strtab;
-			s += strscpy(s,
-				     &rcu_dereference_sched(mod->kallsyms)->strtab[src[i].st_name],
-				     KSYM_NAME_LEN) + 1;
+			ret = strscpy(s,
+				      &rcu_dereference(mod->kallsyms)->strtab[src[i].st_name],
+				      strtab_size);
+			if (ret < 0)
+				break;
+			s += ret + 1;
+			strtab_size -= ret + 1;
 		}
 	}
-	preempt_enable();
+	rcu_read_unlock();
 	mod->core_kallsyms.num_symtab = ndst;
 }
 

kernel/module/main.c

@@ -2939,24 +2939,25 @@ static void cfi_init(struct module *mod)
 {
 #ifdef CONFIG_CFI_CLANG
 	initcall_t *init;
+#ifdef CONFIG_MODULE_UNLOAD
 	exitcall_t *exit;
+#endif
 
 	rcu_read_lock_sched();
 	mod->cfi_check = (cfi_check_fn)
 		find_kallsyms_symbol_value(mod, "__cfi_check");
 	init = (initcall_t *)
 		find_kallsyms_symbol_value(mod, "__cfi_jt_init_module");
-	exit = (exitcall_t *)
-		find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module");
-	rcu_read_unlock_sched();
-
 	/* Fix init/exit functions to point to the CFI jump table */
 	if (init)
 		mod->init = *init;
 #ifdef CONFIG_MODULE_UNLOAD
+	exit = (exitcall_t *)
+		find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module");
 	if (exit)
 		mod->exit = *exit;
 #endif
+	rcu_read_unlock_sched();
 
 	cfi_module_add(mod, mod_tree.addr_min);
 #endif