cgroups: fix potential nullderef

The child_path variable is initialized very late in the function so jumping to
the on_error label would cause a nullderef. With the cleanup macros we can
simplify this function to simply do direct returns and avoid that whole issue.

Closes #2935.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index e40b8079a18ede6c4ce0ecc50b9c7c5218b3fa9a..8c3600bb903045f8cb970f145b69c84e2e29d7ea 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -522,13 +522,17 @@ static bool copy_parent_file(char *path, char *file)
        *lastslash = '\0';
        parent_path = must_make_path(path, file, NULL);
        len = lxc_read_from_file(parent_path, NULL, 0);
-       if (len <= 0)
-               goto on_error;
+       if (len <= 0) {
+               SYSERROR("Failed to determine buffer size");
+               return false;
+       }
 
        value = must_realloc(NULL, len + 1);
        ret = lxc_read_from_file(parent_path, value, len);
-       if (ret != len)
-               goto on_error;
+       if (ret != len) {
+               SYSERROR("Failed to read from parent file \"%s\"", parent_path);
+               return false;
+       }
 
        *lastslash = oldv;
        child_path = must_make_path(path, file, NULL);
@@ -536,10 +540,6 @@ static bool copy_parent_file(char *path, char *file)
        if (ret < 0)
                SYSERROR("Failed to write \"%s\" to file \"%s\"", value, child_path);
        return ret >= 0;
-
-on_error:
-       SYSERROR("Failed to read file \"%s\"", child_path);
-       return false;
 }
 
 /* Initialize the cpuset hierarchy in first directory of @gname and set