Re: [PATCH 2/4] NFS: Move the flock open mode check into nfs_flock()

[Jeff Layton <jlayton@redhat.com>]

On Tue, 2017-02-21 at 10:39 -0500, Benjamin Coddington wrote:
> We only need to check lock exclusive/shared types against open mode when
> flock() is used on NFS, so move it into the flock-specific path instead of
> checking it for all locks.
> 
> Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/nfs/file.c     | 18 ++++++++++++++++--
>  fs/nfs/nfs4proc.c | 14 --------------
>  2 files changed, 16 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index 26dbe8b0c10d..a490f45df4db 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -820,9 +820,23 @@ int nfs_flock(struct file *filp, int cmd, struct file_lock *fl)
>  	if (NFS_SERVER(inode)->flags & NFS_MOUNT_LOCAL_FLOCK)
>  		is_local = 1;
>  
> -	/* We're simulating flock() locks using posix locks on the server */
> -	if (fl->fl_type == F_UNLCK)
> +	/*
> +	 * VFS doesn't require the open mode to match a flock() lock's type.
> +	 * NFS, however, may simulate flock() locking with posix locking which
> +	 * requires the open mode to match the lock type.
> +	 */
> +	switch (fl->fl_type) {
> +	case F_UNLCK:
>  		return do_unlk(filp, cmd, fl, is_local);
> +	case F_RDLCK:
> +		if (!(filp->f_mode & FMODE_READ))
> +			return -EBADF;
> +		break;
> +	case F_WRLCK:
> +		if (!(filp->f_mode & FMODE_WRITE))
> +			return -EBADF;
> +	}
> +
>  	return do_setlk(filp, cmd, fl, is_local);
>  }
>  EXPORT_SYMBOL_GPL(nfs_flock);
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 9388899e4050..91f88bfbbe79 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -6592,20 +6592,6 @@ nfs4_proc_lock(struct file *filp, int cmd, struct file_lock *request)
>  	    !test_bit(NFS_STATE_POSIX_LOCKS, &state->flags))
>  		return -ENOLCK;
>  
> -	/*
> -	 * Don't rely on the VFS having checked the file open mode,
> -	 * since it won't do this for flock() locks.
> -	 */
> -	switch (request->fl_type) {
> -	case F_RDLCK:
> -		if (!(filp->f_mode & FMODE_READ))
> -			return -EBADF;
> -		break;
> -	case F_WRLCK:
> -		if (!(filp->f_mode & FMODE_WRITE))
> -			return -EBADF;
> -	}
> -
>  	status = nfs4_set_lock_state(state, request);
>  	if (status != 0)
>  		return status;

Reviewed-by: Jeff Layton <jlayton@redhat.com>