Re: [RFC PATCH 8/9] orangefs: use set/clear_fs_page_private

Dave Chinner
2020-04-26T22:25:02Z

On Sun, Apr 26, 2020 at 11:49:24PM +0200, Guoqing Jiang wrote:
> Since the new pair function is introduced, we can call them to clean the
> code in orangefs.
>
> Cc: Mike Marshall <hubcap@omnibond.com>
> Cc: Martin Brandenburg <martin@omnibond.com>
> Cc: devel@lists.orangefs.org
> Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
> ---
> fs/orangefs/inode.c | 24 ++++++------------------
> 1 file changed, 6 insertions(+), 18 deletions(-)
>
> diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
> index 12ae630fbed7..893099d36e20 100644
> --- a/fs/orangefs/inode.c
> +++ b/fs/orangefs/inode.c
> @@ -64,9 +64,7 @@ static int orangefs_writepage_locked(struct page *page,
> }
> if (wr) {
> kfree(wr);
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> - put_page(page);
> + clear_fs_page_private(page);

THis is a pre-existing potential use-after-free vector. The wr
pointer held in the page->private needs to be cleared from the page
before it is freed.

> }
> return ret;
> }
> @@ -409,9 +407,7 @@ static int orangefs_write_begin(struct file *file,
> wr->len = len;
> wr->uid = current_fsuid();
> wr->gid = current_fsgid();
> - SetPagePrivate(page);
> - set_page_private(page, (unsigned long)wr);
> - get_page(page);
> + set_fs_page_private(page, wr);
> okay:
> return 0;
> }
> @@ -460,17 +456,13 @@ static void orangefs_invalidatepage(struct page *page,
>
> if (offset == 0 && length == PAGE_SIZE) {
> kfree((struct orangefs_write_range *)page_private(page));
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> - put_page(page);
> + clear_fs_page_private(page);

Ditto:
wr = clear_fs_page_private(page);
kfree(wr);

> return;
> /* write range entirely within invalidate range (or equal) */
> } else if (page_offset(page) + offset <= wr->pos &&
> wr->pos + wr->len <= page_offset(page) + offset + length) {
> kfree((struct orangefs_write_range *)page_private(page));
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> - put_page(page);
> + clear_fs_page_private(page);

And again.

> /* XXX is this right? only caller in fs */
> cancel_dirty_page(page);
> return;
> @@ -537,9 +529,7 @@ static void orangefs_freepage(struct page *page)
> {
> if (PagePrivate(page)) {
> kfree((struct orangefs_write_range *)page_private(page));
> - set_page_private(page, 0);
> - ClearPagePrivate(page);
> - put_page(page);
> + clear_fs_page_private(page);

And again.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com