linux-kernel - [PATCH 4.4 102/312] xprtrdma: xprt_rdma_free() must not release backchannel reqs

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Message-Id: <20200508123131.690727201@linuxfoundation.org>
Date:   Fri,  8 May 2020 14:31:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>,
        Devesh Sharma <devesh.sharma@...gotech.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>
Subject: [PATCH 4.4 102/312] xprtrdma: xprt_rdma_free() must not release backchannel reqs

From: Chuck Lever <chuck.lever@...cle.com>

commit ffc4d9b1596c34caa98962722e930e97912c8a9f upstream.

Preserve any rpcrdma_req that is attached to rpc_rqst's allocated
for the backchannel. Otherwise, after all the pre-allocated
backchannel req's are consumed, incoming backward calls start
writing on freed memory.

Somehow this hunk got lost.

Fixes: f531a5dbc451 ('xprtrdma: Pre-allocate backward rpc_rqst')
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Tested-by: Devesh Sharma <devesh.sharma@...gotech.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/sunrpc/xprtrdma/transport.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/sunrpc/xprtrdma/transport.c
+++ b/net/sunrpc/xprtrdma/transport.c
@@ -576,6 +576,9 @@ xprt_rdma_free(void *buffer)
 
 	rb = container_of(buffer, struct rpcrdma_regbuf, rg_base[0]);
 	req = rb->rg_owner;
+	if (req->rl_backchannel)
+		return;
+
 	r_xprt = container_of(req->rl_buffer, struct rpcrdma_xprt, rx_buf);
 
 	dprintk("RPC:       %s: called on 0x%p\n", __func__, req->rl_reply);