Re: [RFC PATCH] btrfs: drop file privileges in btrfs_clone_files

[Nikolay Borisov <nborisov@suse.com>]

On 28.11.18 г. 5:07 ч., Lu Fengqi wrote:
> The generic/513 tell that cloning into a file did not strip security
> privileges (suid, capabilities) like a regular write would.
> 
> Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
> ---
> The xfs and ocfs2 call generic_remap_file_range_prep to drop file
> privileges, I'm not sure whether btrfs should do the same thing.

Why do you think btrfs shouldn't do the same thing. Looking at
remap_file_range_prep it seems that btrfs is missing a ton of checks
that are useful i.e immutable files/aligned offsets etc.


> 
> Any suggestion?
> 
>  fs/btrfs/ioctl.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 410c7e007ba8..bc33c480603b 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4312,6 +4312,10 @@ static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
>  			goto out_unlock;
>  	}
>  
> +	ret = file_remove_privs(file);
> +	if (ret)
> +		goto out_unlock;
> +
>  	if (destoff > inode->i_size) {
>  		ret = btrfs_cont_expand(inode, inode->i_size, destoff);
>  		if (ret)
>