Re: [PATCH 04/29] xfs: use strndup_user in XFS_IOC_ATTRMULTI_BY_HANDLE

From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org,
	Allison Collins <allison.henderson@oracle.com>
Subject: Re: [PATCH 04/29] xfs: use strndup_user in XFS_IOC_ATTRMULTI_BY_HANDLE
Date: Tue, 21 Jan 2020 09:45:55 -0800	[thread overview]
Message-ID: <20200121174555.GE8247@magnolia> (raw)
In-Reply-To: <20200114081051.297488-5-hch@lst.de>

On Tue, Jan 14, 2020 at 09:10:26AM +0100, Christoph Hellwig wrote:
> Simplify the user copy code by using strndup_user.  This means that we
> now do one memory allocation per operation instead of one per ioctl,
> but memory allocations are cheap compared to the actual file system
> operations.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_ioctl.c   | 17 +++++------------
>  fs/xfs/xfs_ioctl32.c | 17 +++++------------
>  2 files changed, 10 insertions(+), 24 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 6bd0684a3528..f4d5c865e29e 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -446,11 +446,6 @@ xfs_attrmulti_by_handle(
>  		goto out_dput;
>  	}
>  
> -	error = -ENOMEM;
> -	attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
> -	if (!attr_name)
> -		goto out_kfree_ops;
> -
>  	error = 0;
>  	for (i = 0; i < am_hreq.opcount; i++) {
>  		if ((ops[i].am_flags & ATTR_ROOT) &&
> @@ -460,12 +455,11 @@ xfs_attrmulti_by_handle(
>  		}
>  		ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
>  
> -		ops[i].am_error = strncpy_from_user((char *)attr_name,
> -				ops[i].am_attrname, MAXNAMELEN);
> -		if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> -			error = -ERANGE;
> -		if (ops[i].am_error < 0)
> +		attr_name = strndup_user(ops[i].am_attrname, MAXNAMELEN);
> +		if (IS_ERR(attr_name)) {
> +			ops[i].am_error = PTR_ERR(attr_name);
>  			break;
> +		}
>  
>  		switch (ops[i].am_opcode) {
>  		case ATTR_OP_GET:
> @@ -496,13 +490,12 @@ xfs_attrmulti_by_handle(
>  		default:
>  			ops[i].am_error = -EINVAL;
>  		}
> +		kfree(attr_name);
>  	}
>  
>  	if (copy_to_user(am_hreq.ops, ops, size))
>  		error = -EFAULT;
>  
> -	kfree(attr_name);
> - out_kfree_ops:
>  	kfree(ops);
>   out_dput:
>  	dput(dentry);
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index 1092c66e48d6..e6a7f619a54c 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -443,11 +443,6 @@ xfs_compat_attrmulti_by_handle(
>  		goto out_dput;
>  	}
>  
> -	error = -ENOMEM;
> -	attr_name = kmalloc(MAXNAMELEN, GFP_KERNEL);
> -	if (!attr_name)
> -		goto out_kfree_ops;
> -
>  	error = 0;
>  	for (i = 0; i < am_hreq.opcount; i++) {
>  		if ((ops[i].am_flags & ATTR_ROOT) &&
> @@ -457,13 +452,12 @@ xfs_compat_attrmulti_by_handle(
>  		}
>  		ops[i].am_flags &= ~ATTR_KERNEL_FLAGS;
>  
> -		ops[i].am_error = strncpy_from_user((char *)attr_name,
> -				compat_ptr(ops[i].am_attrname),
> +		attr_name = strndup_user(compat_ptr(ops[i].am_attrname),
>  				MAXNAMELEN);
> -		if (ops[i].am_error == 0 || ops[i].am_error == MAXNAMELEN)
> -			error = -ERANGE;
> -		if (ops[i].am_error < 0)
> +		if (IS_ERR(attr_name)) {
> +			ops[i].am_error = PTR_ERR(attr_name);
>  			break;
> +		}
>  
>  		switch (ops[i].am_opcode) {
>  		case ATTR_OP_GET:
> @@ -494,13 +488,12 @@ xfs_compat_attrmulti_by_handle(
>  		default:
>  			ops[i].am_error = -EINVAL;
>  		}
> +		kfree(attr_name);
>  	}
>  
>  	if (copy_to_user(compat_ptr(am_hreq.ops), ops, size))
>  		error = -EFAULT;
>  
> -	kfree(attr_name);
> - out_kfree_ops:
>  	kfree(ops);
>   out_dput:
>  	dput(dentry);
> -- 
> 2.24.1
> 