io_uring: free iovec if file assignment fails

We just return failure in this case, but we need to release the iovec
first. If we're doing IO with more than FAST_IOV segments, then the
iovec is allocated and must be freed.

Reported-by: syzbot+96b43810dfe9c3bb95ed@syzkaller.appspotmail.com
Fixes: 584b0180 ("io_uring: move read/write file prep state into actual opcode handler")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3832,8 +3832,10 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
 		iovec = NULL;
 	}
 	ret = io_rw_init_file(req, FMODE_READ);
-	if (unlikely(ret))
+	if (unlikely(ret)) {
+		kfree(iovec);
 		return ret;
+	}
 	req->result = iov_iter_count(&s->iter);
 
 	if (force_nonblock) {
@@ -3958,8 +3960,10 @@ static int io_write(struct io_kiocb *req, unsigned int issue_flags)
 		iovec = NULL;
 	}
 	ret = io_rw_init_file(req, FMODE_WRITE);
-	if (unlikely(ret))
+	if (unlikely(ret)) {
+		kfree(iovec);
 		return ret;
+	}
 	req->result = iov_iter_count(&s->iter);
 
 	if (force_nonblock) {