lib/iov_iter: initialize "flags" in new pipe_buffer

lib/iov_iter: initialize "flags" in new pipe_buffer

commit 9d2231c5d74e13b2a0546fee6737ee4446017903 upstream.

The functions copy_page_to_iter_pipe() and push_pipe() can both
allocate a new pipe_buffer, but the "flags" member initializer is
missing.

Fixes: 241699cd72a8 ("new iov_iter flavour: pipe-backed")
To: Alexander Viro <viro@zeniv.linux.org.uk>
To: linux-fsdevel@vger.kernel.org
To: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sw0312.kim: chery-pick linux-5.10.y stable commit b19ec7afa929 to resolve CVE-2022-0847]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: Ie8e16157cca8dc16f9b1f222889aa8ed15c281b9