On Mon, 2018-01-15 at 18:30 +0100, Max Kellermann wrote:
> nfs/super: set MS_POSIXACL only if ACL support is enabled
>
> The code comment says "We will [apply the umask] ourselves", but that
> happens in posix_acl_create() only if the kernel has POSIX ACL
> support. Without it, posix_acl_create() is a is an empty dummy
> function.
>
> So let's not pretend we will apply the umask if we can already know
> that we will never.
>
> This fixes a problem where the umask is always ignored in the NFS
> client when compiled without CONFIG_FS_POSIX_ACL. This is a 4 year
> old regression caused by commit 013cdf1088d723 which itself was not
> completely wrong, but failed to consider all the side effects by
> misdesigned VFS code.
>
> There are two compile-time checks and one runtime check:
>
> - If CONFIG_FS_POSIX_ACL=n, then MS_POSIXACL is never set.
>
> - If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=n, then only NFSv4
> has ACL support (and cannot be disabled), and we need to check for
> "version==4".
>
> - If CONFIG_FS_POSIX_ACL=y and CONFIG_NFS_V3_ACL=y, MS_POSIXACL is
> always set, as before.
>
> Signed-off-by: Max Kellermann <mk@xxxxxxxxxx>
> ---
> fs/nfs/super.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> index 216f67d628b3..ec4e1f2775e0 100644
> --- a/fs/nfs/super.c
> +++ b/fs/nfs/super.c
> @@ -2338,10 +2338,17 @@ void nfs_fill_super(struct super_block *sb,
> struct nfs_mount_info *mount_info)
> sb->s_blocksize = nfs_block_size(data->bsize, &sb-
> >s_blocksize_bits);
>
> if (server->nfs_client->rpc_ops->version != 2) {
> - /* The VFS shouldn't apply the umask to mode bits.
> We will do
> - * so ourselves when necessary.
> - */
> - sb->s_flags |= MS_POSIXACL;
> +#ifdef CONFIG_FS_POSIX_ACL
> +#ifndef CONFIG_NFS_V3_ACL
> + if (nfss->nfs_client->rpc_ops->version == 4)
> +#endif
> + /* The VFS shouldn't apply the umask to mode
> + * bits. We will do so ourselves when
> + * necessary.
> + */
> + sb->s_flags |= MS_POSIXACL;
> +#endif
> +
> sb->s_time_gran = 1;
> sb->s_export_op = &nfs_export_ops;
> }
The above illustrates exactly why I've asked people _never_ to make
anything conditional on rpc_ops->version. Please use a NFS capability
(i.e. NFS_SB(sb)->caps) for this kind of thing. That expresses the
condition in terms of the functionality we want instead of a whimsical
protocol version number.
Thanks
Trond
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
