svcrdma: backchannel cannot share a page for send and rcv buffers

The underlying transport releases the page pointed to by rq_buffer
during xprt_rdma_bc_send_request. When the backchannel reply arrives,
rq_rbuffer then points to freed memory.

Fixes: 68778945e46f ('SUNRPC: Separate buffer pointers for RPC ...')
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
index fc4535ead7c2..20027f8de129 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
@@ -177,19 +177,26 @@ xprt_rdma_bc_allocate(struct rpc_task *task)
                 return -EINVAL;
         }
 
+        /* svc_rdma_sendto releases this page */
         page = alloc_page(RPCRDMA_DEF_GFP);
         if (!page)
                 return -ENOMEM;
-
         rqst->rq_buffer = page_address(page);
-        rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
+
+        rqst->rq_rbuffer = kmalloc(rqst->rq_rcvsize, RPCRDMA_DEF_GFP);
+        if (!rqst->rq_rbuffer) {
+                put_page(page);
+                return -ENOMEM;
+        }
         return 0;
 }
 
 static void
 xprt_rdma_bc_free(struct rpc_task *task)
 {
-        /* No-op: ctxt and page have already been freed. */
+        struct rpc_rqst *rqst = task->tk_rqstp;
+
+        kfree(rqst->rq_rbuffer);
 }
 
 static int