lib/iov_iter: initialize "flags" in new pipe_buffer

mainline inclusion
from mainline-v5.17-rc6
commit 9d2231c5
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4WUKP?from=project-issue
CVE: CVE-2022-0847

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/lib/iov_iter.c?id=9d2231c5d74e13b2a0546fee6737ee4446017903

--------------------------------

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: 241699cd ("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: NMax Kellermann <max.kellermann@ionos.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NZhihao Cheng <chengzhihao1@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

lib/iov_iter.c

@@ -407,6 +407,7 @@ static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t by
 		return 0;
 
 	buf->ops = &page_cache_pipe_buf_ops;
+	buf->flags = 0;
 	get_page(page);
 	buf->page = page;
 	buf->offset = offset;
@@ -543,6 +544,7 @@ static size_t push_pipe(struct iov_iter *i, size_t size,
 			break;
 
 		buf->ops = &default_pipe_buf_ops;
+		buf->flags = 0;
 		buf->page = page;
 		buf->offset = 0;
 		buf->len = min_t(ssize_t, left, PAGE_SIZE);