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From:   zhenwei pi <pizhenwei@bytedance.com>
To:     kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, axboe@fb.com
Cc:     linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
        pizhenwei@bytedance.com
Subject: [PATCH] nvme-rdma: handle nvme completion data length
Date:   Thu, 22 Oct 2020 16:38:50 +0800
Message-Id: <20201022083850.1334880-1-pizhenwei@bytedance.com>
Precedence: bulk

Hit a kernel warning:
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 0 at lib/refcount.c:28

RIP: 0010:refcount_warn_saturate+0xd9/0xe0
Call Trace:
 <IRQ>
 nvme_rdma_recv_done+0xf3/0x280 [nvme_rdma]
 __ib_process_cq+0x76/0x150 [ib_core]
 ...

The reason is that a zero bytes message received from target, and the
host side continues to process without length checking, then the
previous CQE is processed twice.

Handle data length, ignore zero bytes message, and try to recovery for
corrupted CQE case.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
---
 drivers/nvme/host/rdma.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/nvme/host/rdma.c b/drivers/nvme/host/rdma.c
index 9e378d0a0c01..9f5112040d43 100644
--- a/drivers/nvme/host/rdma.c
+++ b/drivers/nvme/host/rdma.c
@@ -1767,6 +1767,17 @@ static void nvme_rdma_recv_done(struct ib_cq *cq, struct ib_wc *wc)
 		return;
 	}
 
+	if (unlikely(!wc->byte_len)) {
+		/* zero bytes message could be ignored */
+		return;
+	} else if (unlikely(wc->byte_len < len)) {
+		/* Corrupted completion, try to recovry */
+		dev_err(queue->ctrl->ctrl.device,
+			"Unexpected nvme completion length(%d)\n", wc->byte_len);
+		nvme_rdma_error_recovery(queue->ctrl);
+		return;
+	}
+
 	ib_dma_sync_single_for_cpu(ibdev, qe->dma, len, DMA_FROM_DEVICE);
 	/*
 	 * AEN requests are special as they don't time out and can
-- 
2.11.0