Re: [PATCH] vfs: allow copy_file_range from a swapfile

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Jun 10, 2019 at 08:26:06PM +0300, Amir Goldstein wrote:
> read(2) is allowed from a swapfile, so copy_file_range(2) should
> be allowed as well.
> 
> Reported-by: Theodore Ts'o <tytso@mit.edu>
> Fixes: 96e6e8f4a68d ("vfs: add missing checks to copy_file_range")
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
> 
> Darrick,
> 
> This fixes the generic/554 issue reported by Ted.

Frankly I think we should go the other way -- non-root doesn't get to
copy from or read from swap files.

--D

> I intend to remove the test case of copy from swap file from
> generic/554, so test is expected to pass with or without this fix.
> But if you wait for next week's xfstests update before applying
> this fix, then at lease maintainer that run current xfstests master
> could use current copy-file-range-fixes branch to pass the tests.
> 
> Thanks,
> Amir.
> 
>  mm/filemap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index aac71aef4c61..f74e5ce7ca50 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3081,7 +3081,7 @@ int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
>  	if (IS_IMMUTABLE(inode_out))
>  		return -EPERM;
>  
> -	if (IS_SWAPFILE(inode_in) || IS_SWAPFILE(inode_out))
> +	if (IS_SWAPFILE(inode_out))
>  		return -ETXTBSY;
>  
>  	/* Ensure offsets don't wrap. */
> -- 
> 2.17.1
>