Re: [PATCH v2] netfs: Miscellaneous fixes

Jeff Layton
2021-04-26T22:17:35Z

On Mon, 2021-04-26 at 22:20 +0100, David Howells wrote:
> Okay, how about the attached, then?
>
> David
> ---
> netfs: Miscellaneous fixes
>
>
>
>
> Fix some miscellaneous things in the new netfs lib[1]:
>
>  (1) The kerneldoc for netfs_readpage() shouldn't say netfs_page().
>
>  (2) netfs_readpage() can get an integer overflow on 32-bit when it
>      multiplies page_index(page) by PAGE_SIZE. It should use
>      page_file_offset() instead.
>
>  (3) netfs_write_begin() should use page_offset() to avoid the same
>      overflow.
>
> Note that netfs_readpage() needs to use page_file_offset() rather than
> page_offset() as it may see swap-over-NFS.
>
> Reported-by: Matthew Wilcox <willy@infradead.org>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Link: https://lore.kernel.org/r/161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk/ [1]
> ---
>  fs/netfs/read_helper.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 1d3b50c5db6d..193841d03de0 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -933,7 +933,7 @@ void netfs_readahead(struct readahead_control *ractl,
>  EXPORT_SYMBOL(netfs_readahead);
>
>
>
>
>  /**
> - * netfs_page - Helper to manage a readpage request
> + * netfs_readpage - Helper to manage a readpage request
>   * @file: The file to read from
>   * @page: The page to read
>   * @ops: The network filesystem's operations for the helper to use
> @@ -968,7 +968,7 @@ int netfs_readpage(struct file *file,
>   return -ENOMEM;
>   }
>   rreq->mapping = page_file_mapping(page);
> - rreq->start = page_index(page) * PAGE_SIZE;
> + rreq->start = page_file_offset(page);
>   rreq->len = thp_size(page);
>
>
>
>
>   if (ops->begin_cache_operation) {
> @@ -1106,7 +1106,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>   if (!rreq)
>   goto error;
>   rreq->mapping = page->mapping;
> - rreq->start = page->index * PAGE_SIZE;
> + rreq->start = page_offset(page);
>   rreq->len = thp_size(page);
>   rreq->no_unlock_page = page->index;
>   __set_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags);
>

Reviewed-by: Jeff Layton <jlayton@kernel.org>