io_uring/net: ensure vectored buffer node import is tied to notification

When support for vectored registered buffers was added, the import
itself is using 'req' rather than the notification io_kiocb, sr->notif.
For non-vectored imports, sr->notif is correctly used. This is important
as the lifetime of the two may be different. Use the correct io_kiocb
for the vectored buffer import.

Cc: stable@vger.kernel.org
Fixes: 23371ea ("io_uring/net: implement vectored reg bufs for zctx")
Reported-by: Google Big Sleep <big-sleep-vuln-reports+bigsleep-463332873@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/net.c

@@ -1532,8 +1532,10 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags)
 		unsigned uvec_segs = kmsg->msg.msg_iter.nr_segs;
 		int ret;
 
-		ret = io_import_reg_vec(ITER_SOURCE, &kmsg->msg.msg_iter, req,
-					&kmsg->vec, uvec_segs, issue_flags);
+		sr->notif->buf_index = req->buf_index;
+		ret = io_import_reg_vec(ITER_SOURCE, &kmsg->msg.msg_iter,
+					sr->notif, &kmsg->vec, uvec_segs,
+					issue_flags);
 		if (unlikely(ret))
 			return ret;
 		req->flags &= ~REQ_F_IMPORT_BUFFER;