On Wed, May 29, 2019 at 08:43:12PM +0300, Amir Goldstein wrote:
> Because generic_copy_file_range doesn't hold the destination inode lock
> throughout the copy, strip setuid bits before and after copy.
>
> The destination inode mtime is updated before and after the copy and the
> source inode atime is updated after the copy, similar to
> generic_file_read_iter().
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Looks reasonable,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/read_write.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index cec7e7b1f693..706ea5f276a7 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1590,8 +1590,27 @@ ssize_t generic_copy_file_range(struct file *file_in, loff_t pos_in,
> struct file *file_out, loff_t pos_out,
> size_t len, unsigned int flags)
> {
> - return do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> - len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> + struct inode *inode_out = file_inode(file_out);
> + int ret, err;
> +
> + /* Should inode_out lock be held throughout the copy operation? */
> + inode_lock(inode_out);
> + err = file_modified(file_out);
> + inode_unlock(inode_out);
> + if (err)
> + return err;
> +
> + ret = do_splice_direct(file_in, &pos_in, file_out, &pos_out,
> + len > MAX_RW_COUNT ? MAX_RW_COUNT : len, 0);
> +
> + file_accessed(file_in);
> +
> + /* To be on the safe side, remove privs also after copy */
> + inode_lock(inode_out);
> + err = file_modified(file_out);
> + inode_unlock(inode_out);
> +
> + return err ?: ret;
> }
> EXPORT_SYMBOL(generic_copy_file_range);
>
> --
> 2.17.1
>
