On Thu, Sep 07, 2023 at 01:32:36PM -0400, Jeff Layton wrote: > In older kernels, attempting to fetch that system.posix_acl_access on > NFSv4 would return -EOPNOTSUPP, but in more recent kernels that returns > -ENODATA. > > Most filesystems that don't support POSIX ACLs leave the SB_POSIXACL > flag clear, which cues the VFS to return -EOPNOTSUPP in this situation. > We can't do that with NFSv4 since that flag also cues the VFS to avoid > applying the umask early. > > Fix this by adding a stub get_acl handler for NFSv4 that always returns > -EOPNOTSUPP. > > Reported-by: Ondrej Valousek <ondrej.valousek.xm@xxxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > I suspect that this problem popped in due to some VFS layer changes. I > haven't identified the patch that broke it, but I think this is probably > the least invasive way to fix it. > > Another alternative would be to return -EOPNOTSUPP on filesystems that > set SB_POSIXACL but that don't set get_acl or get_inode_acl. > > Thoughts? Yes: I hate POSIX ACLs. ;) Before the VFS rework to only rely on i_op->*acl* methods POSIX ACLs were set using sb->s_xattr handlers. So when a filesystem raised SB_POSIXACL but didn't set sb->s_xattr handlers for POSIX ACLs we would: __vfs_getxattr() -> xattr_resolve_name() // no match so return EOPNOTSUPP No we have vfs_get_acl() -> __get_acl() -> i_op->get_acl // no get_acl inode method return ENODATA So as a bugfix to backport I think you should do exactly what you do here because I'm not sure if some fs relies on ENODATA to be returned if no get_acl inode method is set. There's a lot of quirkiness everywhere. But we should look through all callers and if nothing relies on EINVAL just start returning EOPNOTSUPP if no get_acl i_op is set. Looks good to me, Acked-by: Christian Brauner <brauner@xxxxxxxxxx>
