nspawn: Simplify mkdir_userns() usage, and trickle that up

LukeShu · LukeShu · commit 9c0fad5fb5f4 · 2018-07-20T12:12:02.000-04:00
One of the things that mkdir_userns{,_p}() does is take an (optional) UID,
and chown the directory to that.  So we need a uid_t argument, and a way of
telling if we should use that uid_t argument.  Fortunately, that is built
in to the uid_t type by having UID_INVALID as a possible value.

However, currently mkdir_userns() also takes a MountSettingsMask and checks
a couple of bits in it to decide if it should perform the chown.

Drop the mask argument, and instead have the caller pass UID_INVALID if it
shouldn't chown.
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
@@ -442,7 +442,7 @@ int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
                              MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
 }
 
-static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
+static int mkdir_userns(const char *path, mode_t mode, uid_t uid_shift) {
         int r;
 
         assert(path);
@@ -451,10 +451,7 @@ static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, u
         if (r < 0 && r != -EEXIST)
                 return r;
 
-        if ((mask & MOUNT_USE_USERNS) == 0)
-                return 0;
-
-        if (mask & MOUNT_IN_USERNS)
+        if (uid_shift == UID_INVALID)
                 return 0;
 
         if (lchown(path, uid_shift, uid_shift) < 0)
@@ -463,7 +460,7 @@ static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, u
         return 0;
 }
 
-static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
+static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, uid_t uid_shift) {
         const char *p, *e;
         int r;
 
@@ -490,12 +487,12 @@ static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, Mou
                 if (prefix && path_startswith(prefix, t))
                         continue;
 
-                r = mkdir_userns(t, mode, mask, uid_shift);
+                r = mkdir_userns(t, mode, uid_shift);
                 if (r < 0)
                         return r;
         }
 
-        return mkdir_userns(path, mode, mask, uid_shift);
+        return mkdir_userns(path, mode, uid_shift);
 }
 
 int mount_all(const char *dest,
@@ -634,7 +631,7 @@ int mount_all(const char *dest,
                 if (what && r > 0)
                         continue;
 
-                r = mkdir_userns_p(dest, where, 0755, mount_settings, uid_shift);
+                r = mkdir_userns_p(dest, where, 0755, (use_userns && !in_userns) ? uid_shift : UID_INVALID);
                 if (r < 0 && r != -EEXIST) {
                         if (fatal && r != -EROFS)
                                 return log_error_errno(r, "Failed to create directory %s: %m", where);
