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@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
cc: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
cc: linux-afs@xxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/162367682522.460125.5652091227576721609.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v1
---
fs/afs/write.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 8e4e87d66855..9db3ddb1c45b 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -120,6 +120,7 @@ int afs_write_end(struct file *file, struct address_space *mapping,
_enter("{%llx:%llu},{%lx}",
vnode->fid.vid, vnode->fid.vnode, folio_index(folio));
+ len = min_t(size_t, len, folio_size(folio) - from);
if (!folio_test_uptodate(folio)) {
if (copied < len) {
copied = 0;
