namespace: don't fail on masked mounts (#3794)

Before this patch, a service file with ReadWriteDirectories=/file...
could fail if the file exists but is not a mountpoint, despite being
listed in /proc/self/mountinfo. It could happen with masked mounts.

Fixes https://github.com/elogind/elogind/issues/3793

diff --git a/src/basic/mount-util.c b/src/basic/mount-util.c
index de12453c5f75e4b37e2133043c7bf330eaf7a636..d04a49e2fef7af05a0ee7c9c6230ef8ba3785ca9 100644 (file)
--- a/src/basic/mount-util.c
+++ b/src/basic/mount-util.c
@@ -449,21 +449,21 @@ int bind_remount_recursive(const char *prefix, bool ro) {
                         if (r < 0)
                                 return r;
 
-                        /* Try to reuse the original flag set, but
-                         * don't care for errors, in case of
-                         * obstructed mounts */
+                        /* Deal with mount points that are obstructed by a
+                         * later mount */
+                        r = path_is_mount_point(x, 0);
+                        if (r == -ENOENT || r == 0)
+                                continue;
+                        if (r < 0)
+                                return r;
+
+                        /* Try to reuse the original flag set */
                         orig_flags = 0;
                         (void) get_mount_flags(x, &orig_flags);
                         orig_flags &= ~MS_RDONLY;
 
-                        if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
-
-                                /* Deal with mount points that are
-                                 * obstructed by a later mount */
-
-                                if (errno != ENOENT)
-                                        return -errno;
-                        }
+                        if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
+                                return -errno;
 
                 }
         }