[PATCH 05/67] afs: Fix afs_write_end() to handle len > page size

David Howells
2021-10-18T14:52:04Z

It is possible for the len argument to afs_write_end() to overrun the end
of the page (len is used to key the size of the page in afs_write_start()
when compound pages become a regular thing).

Fix afs_write_end() to correctly trim the write length so that it doesn't
exceed the end of the page.

Fixes: 3003bbd0697b ("afs: Use the netfs_write_begin() helper")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/162367682522.460125.5652091227576721609.stgit@warthog.procyon.org.uk/ # v1
---

fs/afs/write.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index c09830c9dc43..e1cb19cb6314 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -119,6 +119,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
_enter("{%llx:%llu},{%lx}",
vnode->fid.vid, vnode->fid.vnode, page->index);

+ len = min_t(size_t, len, thp_size(page) - from);
if (!PageUptodate(page)) {
if (copied < len) {
copied = 0;