ovl: Prevent rw remount when it should be ro mount (3cdf6fe9) · Commits · 戴 / test

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>

fs/overlayfs/super.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -525,10 +525,22 @@ static int ovl_show_options(struct seq_file m, struct dentry dentry)
		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 {

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