io-wq: Fix memory leak in worker creation

If the CPU mask allocation for a node fails, then the memory allocated for
the 'io_wqe' struct of the current node doesn't get freed on the error
handling path, since it has not yet been added to the 'wqes' array.

This was spotted when fuzzing v6.1-rc1 with Syzkaller:
BUG: memory leak
unreferenced object 0xffff8880093d5000 (size 1024):
  comm "syz-executor.2", pid 7701, jiffies 4295048595 (age 13.900s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000cb463369>] __kmem_cache_alloc_node+0x18e/0x720
    [<00000000147a3f9c>] kmalloc_node_trace+0x2a/0x130
    [<000000004e107011>] io_wq_create+0x7b9/0xdc0
    [<00000000c38b2018>] io_uring_alloc_task_context+0x31e/0x59d
    [<00000000867399da>] __io_uring_add_tctx_node.cold+0x19/0x1ba
    [<000000007e0e7a79>] io_uring_setup.cold+0x1b80/0x1dce
    [<00000000b545e9f6>] __x64_sys_io_uring_setup+0x5d/0x80
    [<000000008a8a7508>] do_syscall_64+0x5d/0x90
    [<000000004ac08bec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 0e03496d19 ("io-wq: use private CPU mask")
Cc: stable@vger.kernel.org
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Link: https://lore.kernel.org/r/20221020014710.902201-1-rafaelmendsr@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/io-wq.c

@@ -1164,10 +1164,10 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 		wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
 		if (!wqe)
 			goto err;
+		wq->wqes[node] = wqe;
 		if (!alloc_cpumask_var(&wqe->cpu_mask, GFP_KERNEL))
 			goto err;
 		cpumask_copy(wqe->cpu_mask, cpumask_of_node(node));
-		wq->wqes[node] = wqe;
 		wqe->node = alloc_node;
 		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
 		wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =