kconfig: do not accept a directory for configuration output

Currently, conf_write() can be called with a directory name instead
of a file name. As far as I see, this can happen for menuconfig,
nconfig, gconfig.

If it is given with a directory path, conf_write() kindly appends
getenv("KCONFIG_CONFIG"), but this ends up with hacky dir/basename
handling, and screwed up in corner-cases like "what if KCONFIG_CONFIG
is an absolute path?" as discussed before:

  https://patchwork.kernel.org/patch/9910037/

Since conf_write() is already messed up, I'd say "do not do it".
Please pass a file path all the time. If a directory path is specified
for the configuration output, conf_write() will simply error out.

Now that the tmp file is created in the same directory as the .config,
the previously reported "what if KCONFIG_CONFIG points to a different
file system?" has been solved.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Nicolas Porcel <nicolasporcel06@gmail.com>

1 files changed, 24 insertions, 34 deletions

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index 08ba146a83c5..9fd6430c93d2 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -817,40 +817,31 @@ 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 (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();
-
-        sprintf(newname, "%s%s", dirname, basename);
+        if (!name)
+                name = conf_get_configname();
+
+        if (!*name) {
+                fprintf(stderr, "config name is empty\n");
+                return -1;
+        }
+
+        if (is_dir(name)) {
+                fprintf(stderr, "%s: Is a directory\n", name);
+                return -1;
+        }
+
         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 +888,13 @@ next:
         fclose(out);
 
         if (*tmpname) {
-                strcat(dirname, basename);
-                strcat(dirname, ".old");
-                rename(newname, dirname);
-                if (rename(tmpname, newname))
+                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);