Re: [PATCH v2 1/1] nfs42: client needs to update file mode after ALLOCATE op

[Trond Myklebust <trondmy@xxxxxxxxxxxxxxx>]

On Thu, 2023-08-24 at 08:53 -0700, Dai Ngo wrote:
> The Linux NFS server strips the SUID and SGID from the file mode
> on ALLOCATE op. The GETATTR op in the ALLOCATE compound needs to
> request the file mode from the server to update its file mode in
> case the SUID/SGUI bit were stripped.
> 
> Signed-off-by: Dai Ngo <dai.ngo@xxxxxxxxxx>
> ---
>  fs/nfs/nfs42proc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> index 63802d195556..d3d050171822 100644
> --- a/fs/nfs/nfs42proc.c
> +++ b/fs/nfs/nfs42proc.c
> @@ -70,7 +70,7 @@ static int _nfs42_proc_fallocate(struct rpc_message
> *msg, struct file *filep,
>         }
>  
>         nfs4_bitmask_set(bitmask, server->cache_consistency_bitmask,
> inode,
> -                        NFS_INO_INVALID_BLOCKS);
> +                       NFS_INO_INVALID_BLOCKS |
> NFS_INO_INVALID_MODE);
>  
>         res.falloc_fattr = nfs_alloc_fattr();
>         if (!res.falloc_fattr)

Actually... Wait... Why isn't the existing code sufficient?

        status = nfs4_call_sync(server->client, server, msg,
                                &args.seq_args, &res.seq_res, 0);
        if (status == 0) {
                if (nfs_should_remove_suid(inode)) {
                        spin_lock(&inode->i_lock);
                        nfs_set_cache_invalid(inode, NFS_INO_INVALID_MODE);
                        spin_unlock(&inode->i_lock);
                }
                status = nfs_post_op_update_inode_force_wcc(inode,
                                                            res.falloc_fattr);
        }

We explicitly check for SUID bits, and invalidate the mode if they are
set.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@xxxxxxxxxxxxxxx