ovl: Prevent rw remount when it should be ro mount
Overlayfs should be mounted read-only when upper-fs is read-only or nonexistent.
But now it can be remounted read-write and this can cause kernel panic.
So we should prevent read-write remount when the above situation happens.
Signed-off-by: Seunghun Lee <waydi1@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9e94f4a..b90952f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -525,10 +525,22 @@
return 0;
}
+static int ovl_remount(struct super_block *sb, int *flags, char *data)
+{
+ struct ovl_fs *ufs = sb->s_fs_info;
+
+ if (!(*flags & MS_RDONLY) &&
+ (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
+ return -EROFS;
+
+ return 0;
+}
+
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
+ .remount_fs = ovl_remount,
};
enum {