linux-ext4 - Re: [PATCH 10/11] fs: remove the access_ok() check in ioctl

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Message-Id: <20200501225635.2DFA4AE045@d06av26.portsmouth.uk.ibm.com>
Date:   Sat, 2 May 2020 04:26:34 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Christoph Hellwig <hch@....de>, linux-ext4@...r.kernel.org,
        viro@...iv.linux.org.uk
Cc:     jack@...e.cz, tytso@....edu, adilger@...ger.ca, amir73il@...il.com,
        linux-fsdevel@...r.kernel.org, linux-unionfs@...r.kernel.org
Subject: Re: [PATCH 10/11] fs: remove the access_ok() check in ioctl_fiemap



On 4/27/20 11:49 PM, Christoph Hellwig wrote:
> access_ok just checks we are fed a proper user pointer.  We also do that
> in copy_to_user itself, so no need to do this early.

Ok.

> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Looks fine. Feel free to add
Reviewed-by: Ritesh Harjani <riteshh@...ux.ibm.com>


> ---
>   fs/ioctl.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index ae0d228d18a16..d24afce649037 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -209,13 +209,9 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
>   	fieinfo.fi_extents_max = fiemap.fm_extent_count;
>   	fieinfo.fi_extents_start = ufiemap->fm_extents;
>   
> -	if (fiemap.fm_extent_count != 0 &&
> -	    !access_ok(fieinfo.fi_extents_start,
> -		       fieinfo.fi_extents_max * sizeof(struct fiemap_extent)))
> -		return -EFAULT;
> -
>   	error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start,
>   			fiemap.fm_length);
> +
>   	fiemap.fm_flags = fieinfo.fi_flags;
>   	fiemap.fm_mapped_extents = fieinfo.fi_extents_mapped;
>   	if (copy_to_user(ufiemap, &fiemap, sizeof(fiemap)))
>