Merge pull request #7910 from poettering/getcwd

some getcwd() fixes, and other path-util tweaks

src/basic/path-util.c

@@ -81,14 +81,36 @@ char *path_make_absolute(const char *p, const char *prefix) {
         /* Makes every item in the list an absolute path by prepending
          * the prefix, if specified and necessary */
 
-        if (path_is_absolute(p) || !prefix)
+        if (path_is_absolute(p) || isempty(prefix))
                 return strdup(p);
 
-        return strjoin(prefix, "/", p);
+        if (endswith(prefix, "/"))
+                return strjoin(prefix, p);
+        else
+                return strjoin(prefix, "/", p);
+}
+
+int safe_getcwd(char **ret) {
+        char *cwd;
+
+        cwd = get_current_dir_name();
+        if (!cwd)
+                return negative_errno();
+
+        /* Let's make sure the directory is really absolute, to protect us from the logic behind
+         * CVE-2018-1000001 */
+        if (cwd[0] != '/') {
+                free(cwd);
+                return -ENOMEDIUM;
+        }
+
+        *ret = cwd;
+        return 0;
 }
 
 int path_make_absolute_cwd(const char *p, char **ret) {
         char *c;
+        int r;
 
         assert(p);
         assert(ret);
@@ -101,11 +123,14 @@ int path_make_absolute_cwd(const char *p, char **ret) {
         else {
                 _cleanup_free_ char *cwd = NULL;
 
-                cwd = get_current_dir_name();
-                if (!cwd)
-                        return negative_errno();
+                r = safe_getcwd(&cwd);
+                if (r < 0)
+                        return r;
 
-                c = strjoin(cwd, "/", p);
+                if (endswith(cwd, "/"))
+                        c = strjoin(cwd, p);
+                else
+                        c = strjoin(cwd, "/", p);
         }
         if (!c)
                 return -ENOMEM;

src/basic/path-util.h

@@ -41,6 +41,7 @@ bool is_path(const char *p) _pure_;
 int path_split_and_make_absolute(const char *p, char ***ret);
 bool path_is_absolute(const char *p) _pure_;
 char* path_make_absolute(const char *p, const char *prefix);
+int safe_getcwd(char **ret);
 int path_make_absolute_cwd(const char *p, char **ret);
 int path_make_relative(const char *from_dir, const char *to_path, char **_r);
 char* path_kill_slashes(char *path);

src/cgls/cgls.c

@@ -277,9 +277,9 @@ int main(int argc, char *argv[]) {
                 if (!arg_machine)  {
                         _cleanup_free_ char *cwd = NULL;
 
-                        cwd = get_current_dir_name();
-                        if (!cwd) {
-                                r = log_error_errno(errno, "Cannot determine current working directory: %m");
+                        r = safe_getcwd(&cwd);
+                        if (r < 0) {
+                                log_error_errno(r, "Cannot determine current working directory: %m");
                                 goto finish;
                         }
 

src/nspawn/nspawn.c

@@ -2163,8 +2163,11 @@ static int determine_names(void) {
 
                         if (!arg_ephemeral)
                                 arg_read_only = arg_read_only || i->read_only;
-                } else
-                        arg_directory = get_current_dir_name();
+                } else {
+                        r = safe_getcwd(&arg_directory);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to determine current directory: %m");
+                }
 
                 if (!arg_directory && !arg_image) {
                         log_error("Failed to determine path, please use -D or -i.");

src/test/test-fs-util.c

@@ -326,7 +326,7 @@ static void test_readlink_and_make_absolute(void) {
         free(r);
         assert_se(unlink(name_alias) >= 0);
 
-        assert_se(pwd = get_current_dir_name());
+        assert_se(safe_getcwd(&pwd) >= 0);
 
         assert_se(chdir(tempdir) >= 0);
         assert_se(symlink(name2, name_alias) >= 0);