afs: Fix the maths in afs_fs_store_data()
afs_fs_store_data() works out of the size of the write it's going to make,
but it uses 32-bit unsigned subtraction in one place that gets
automatically cast to loff_t.
However, if to < offset, then the number goes negative, but as the result
isn't signed, this doesn't get sign-extended to 64-bits when placed in a
loff_t.
Fix by casting the operands to loff_t.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 0778c5b..d9234b7 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -1236,7 +1236,7 @@ int afs_fs_store_data(struct afs_server *server, struct afs_writeback *wb,
_enter(",%x,{%x:%u},,",
key_serial(wb->key), vnode->fid.vid, vnode->fid.vnode);
- size = to - offset;
+ size = (loff_t)to - (loff_t)offset;
if (first != last)
size += (loff_t)(last - first) << PAGE_SHIFT;
pos = (loff_t)first << PAGE_SHIFT;