[PATCH v2] netfs: Miscellaneous fixes

David Howells
2021-04-26T21:20:15Z

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);