Kconfig updates for v5.2

- error out if a user specifies a directory instead of a file from
    "Save" menu of GUI interfaces
 
  - do not overwrite .config if there is no change in the configuration
 
  - create parent directories as needed when a user specifies a new file
    path from "Save" menu of menuconfig/nconfig
 
  - fix potential buffer overflow
 
  - some trivial cleanups
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Merge tag 'kconfig-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kconfig updates from Masahiro Yamada:

 - error out if a user specifies a directory instead of a file from
   "Save" menu of GUI interfaces

 - do not overwrite .config if there is no change in the configuration

 - create parent directories as needed when a user specifies a new file
   path from "Save" menu of menuconfig/nconfig

 - fix potential buffer overflow

 - some trivial cleanups

* tag 'kconfig-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: make conf_get_autoconfig_name() static
  kconfig: use snprintf for formatting pathnames
  kconfig: remove useless NULL pointer check in conf_write_dep()
  kconfig: make parent directories for the saved .config as needed
  kconfig: do not write .config if the content is the same
  kconfig: do not accept a directory for configuration output
  kconfig: remove trailing whitespaces
  kconfig: Make nconf-cfg.sh executable

scripts/kconfig/confdata.c

@@ -3,6 +3,7 @@
  * Copyright (C) 2002 Roman Zippel <zippel@linux-m68k.org>
  */
 
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <ctype.h>
 #include <errno.h>
@@ -36,6 +37,52 @@ static bool is_dir(const char *path)
 	return S_ISDIR(st.st_mode);
 }
 
+/* return true if the given two files are the same, false otherwise */
+static bool is_same(const char *file1, const char *file2)
+{
+	int fd1, fd2;
+	struct stat st1, st2;
+	void *map1, *map2;
+	bool ret = false;
+
+	fd1 = open(file1, O_RDONLY);
+	if (fd1 < 0)
+		return ret;
+
+	fd2 = open(file2, O_RDONLY);
+	if (fd2 < 0)
+		goto close1;
+
+	ret = fstat(fd1, &st1);
+	if (ret)
+		goto close2;
+	ret = fstat(fd2, &st2);
+	if (ret)
+		goto close2;
+
+	if (st1.st_size != st2.st_size)
+		goto close2;
+
+	map1 = mmap(NULL, st1.st_size, PROT_READ, MAP_PRIVATE, fd1, 0);
+	if (map1 == MAP_FAILED)
+		goto close2;
+
+	map2 = mmap(NULL, st2.st_size, PROT_READ, MAP_PRIVATE, fd2, 0);
+	if (map2 == MAP_FAILED)
+		goto close2;
+
+	if (bcmp(map1, map2, st1.st_size))
+		goto close2;
+
+	ret = true;
+close2:
+	close(fd2);
+close1:
+	close(fd1);
+
+	return ret;
+}
+
 /*
  * Create the parent directory of the given path.
  *
@@ -179,7 +226,7 @@ const char *conf_get_configname(void)
 	return name ? name : ".config";
 }
 
-const char *conf_get_autoconfig_name(void)
+static const char *conf_get_autoconfig_name(void)
 {
 	char *name = getenv("KCONFIG_AUTOCONFIG");
 
@@ -194,7 +241,7 @@ char *conf_get_default_confname(void)
 	name = expand_string(conf_defname);
 	env = getenv(SRCTREE);
 	if (env) {
-		sprintf(fullname, "%s/%s", env, name);
+		snprintf(fullname, sizeof(fullname), "%s/%s", env, name);
 		if (is_present(fullname))
 			return fullname;
 	}
@@ -817,40 +864,34 @@ int conf_write(const char *name)
 	FILE *out;
 	struct symbol *sym;
 	struct menu *menu;
-	const char *basename;
 	const char *str;
-	char dirname[PATH_MAX+1], tmpname[PATH_MAX+22], newname[PATH_MAX+8];
+	char tmpname[PATH_MAX + 1], oldname[PATH_MAX + 1];
 	char *env;
 
-	dirname[0] = 0;
-	if (name && name[0]) {
-		char *slash;
+	if (!name)
+		name = conf_get_configname();
+
+	if (!*name) {
+		fprintf(stderr, "config name is empty\n");
+		return -1;
+	}
 
 	if (is_dir(name)) {
-			strcpy(dirname, name);
-			strcat(dirname, "/");
-			basename = conf_get_configname();
-		} else if ((slash = strrchr(name, '/'))) {
-			int size = slash - name + 1;
-			memcpy(dirname, name, size);
-			dirname[size] = 0;
-			if (slash[1])
-				basename = slash + 1;
-			else
-				basename = conf_get_configname();
-		} else
-			basename = name;
-	} else
-		basename = conf_get_configname();
+		fprintf(stderr, "%s: Is a directory\n", name);
+		return -1;
+	}
+
+	if (make_parent_dir(name))
+		return -1;
 
-	sprintf(newname, "%s%s", dirname, basename);
 	env = getenv("KCONFIG_OVERWRITECONFIG");
-	if (!env || !*env) {
-		sprintf(tmpname, "%s.tmpconfig.%d", dirname, (int)getpid());
-		out = fopen(tmpname, "w");
-	} else {
+	if (env && *env) {
 		*tmpname = 0;
-		out = fopen(newname, "w");
+		out = fopen(name, "w");
+	} else {
+		snprintf(tmpname, sizeof(tmpname), "%s.%d.tmp",
+			 name, (int)getpid());
+		out = fopen(tmpname, "w");
 	}
 	if (!out)
 		return 1;
@@ -897,14 +938,20 @@ next:
 	fclose(out);
 
 	if (*tmpname) {
-		strcat(dirname, basename);
-		strcat(dirname, ".old");
-		rename(newname, dirname);
-		if (rename(tmpname, newname))
+		if (is_same(name, tmpname)) {
+			conf_message("No change to %s", name);
+			unlink(tmpname);
+			sym_set_change_count(0);
+			return 0;
+		}
+
+		snprintf(oldname, sizeof(oldname), "%s.old", name);
+		rename(name, oldname);
+		if (rename(tmpname, name))
 			return 1;
 	}
 
-	conf_message("configuration written to %s", newname);
+	conf_message("configuration written to %s", name);
 
 	sym_set_change_count(0);
 
@@ -917,8 +964,6 @@ static int conf_write_dep(const char *name)
 	struct file *file;
 	FILE *out;
 
-	if (!name)
-		name = ".kconfig.d";
 	out = fopen("..config.tmp", "w");
 	if (!out)
 		return 1;

scripts/kconfig/lexer.l

@@ -378,7 +378,8 @@ FILE *zconf_fopen(const char *name)
 	if (!f && name != NULL && name[0] != '/') {
 		env = getenv(SRCTREE);
 		if (env) {
-			sprintf(fullname, "%s/%s", env, name);
+			snprintf(fullname, sizeof(fullname),
+				 "%s/%s", env, name);
 			f = fopen(fullname, "r");
 		}
 	}

scripts/kconfig/lkc.h

@@ -49,7 +49,6 @@ const char *zconf_curname(void);
 
 /* confdata.c */
 const char *conf_get_configname(void);
-const char *conf_get_autoconfig_name(void);
 char *conf_get_default_confname(void);
 void sym_set_change_count(int count);
 void sym_add_change_count(int count);

scripts/kconfig/mconf.c

@@ -936,7 +936,7 @@ static void conf_save(void)
 				set_config_filename(dialog_input_result);
 				return;
 			}
-			show_textbox(NULL, "Can't create file!  Probably a nonexistent directory.", 5, 60);
+			show_textbox(NULL, "Can't create file!", 5, 60);
 			break;
 		case 1:
 			show_helptext("Save Alternate Configuration", save_config_help);

scripts/kconfig/nconf.c

@@ -1438,8 +1438,7 @@ static void conf_save(void)
 				set_config_filename(dialog_input_result);
 				return;
 			}
-			btn_dialog(main_window, "Can't create file! "
-				"Probably a nonexistent directory.",
+			btn_dialog(main_window, "Can't create file!",
 				1, "<OK>");
 			break;
 		case 1: