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

3 files changed, 35 insertions, 22 deletions

diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index bc5507ab8450..ec104c2950c3 100644
--- a/kernel/module/internal.h
+++ b/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;
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index 3e11523bc6f6..77e75bead569 100644
--- a/kernel/module/kallsyms.c
+++ b/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;
 }
 
diff --git a/kernel/module/main.c b/kernel/module/main.c
index fed58d30725d..0548151dd933 100644
--- a/kernel/module/main.c
+++ b/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