From: Valerie Aurora <vaurora@xxxxxxxxxx> A remount request must not (a) convert a union to a non-union (or vice versa), or (b) make the topmost layer of a union read-only. Note that we only have to worry about attempts to remount the vfsmount of the topmost read-write of the union (the one with MNT_UNION set). The vfsmounts of the read-only layers are hidden in a cloned tree hanging of the superblock of the topmost layer and aren't visible to userspace. Original-author: Valerie Aurora <vaurora@xxxxxxxxxx> Signed-off-by: David Howells <dhowells@xxxxxxxxxx> --- fs/namespace.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 261944d..aa6b1ef 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1907,6 +1907,18 @@ static int do_remount(struct path *path, int flags, int mnt_flags, if (!check_mnt(mnt)) return -EINVAL; + if ((path->mnt->mnt_flags & MNT_UNION) && + !(mnt_flags & MNT_UNION)) + return -EINVAL; + + if ((mnt_flags & MNT_UNION) && + !(path->mnt->mnt_flags & MNT_UNION)) + return -EINVAL; + + if ((path->mnt->mnt_flags & MNT_UNION) && + (mnt_flags & MNT_READONLY)) + return -EINVAL; + if (path->dentry != path->mnt->mnt_root) return -EINVAL; -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
