linux-kernel - [PATCH 3.4 008/176] SUNRPC: Fix locking around callback channel reply receive

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Message-Id: <1428569224-23820-8-git-send-email-lizf@kernel.org>
Date:	Thu,  9 Apr 2015 16:44:16 +0800
From:	lizf@...nel.org
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	"J. Bruce Fields" <bfields@...hat.com>,
	Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3.4 008/176] SUNRPC: Fix locking around callback channel reply receive

From: Trond Myklebust <trond.myklebust@...marydata.com>

3.4.107-rc1 review patch.  If anyone has any objections, please let me know.

------------------


commit 093a1468b6edb0e568be7311b8d2228d205702db upstream.

Both xprt_lookup_rqst() and xprt_complete_rqst() require that you
take the transport lock in order to avoid races with xprt_transmit().

Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Reviewed-by: Jeff Layton <jlayton@...marydata.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@...wei.com>
---
 net/sunrpc/svcsock.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 4c23cfc..a0769e1 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1055,17 +1055,12 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	xid = *p++;
 	calldir = *p;
 
-	if (bc_xprt)
-		req = xprt_lookup_rqst(bc_xprt, xid);
-
-	if (!req) {
-		printk(KERN_NOTICE
-			"%s: Got unrecognized reply: "
-			"calldir 0x%x xpt_bc_xprt %p xid %08x\n",
-			__func__, ntohl(calldir),
-			bc_xprt, xid);
+	if (!bc_xprt)
 		return -EAGAIN;
-	}
+	spin_lock_bh(&bc_xprt->transport_lock);
+	req = xprt_lookup_rqst(bc_xprt, xid);
+	if (!req)
+		goto unlock_notfound;
 
 	memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
 	/*
@@ -1076,11 +1071,21 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
 	dst = &req->rq_private_buf.head[0];
 	src = &rqstp->rq_arg.head[0];
 	if (dst->iov_len < src->iov_len)
-		return -EAGAIN; /* whatever; just giving up. */
+		goto unlock_eagain; /* whatever; just giving up. */
 	memcpy(dst->iov_base, src->iov_base, src->iov_len);
 	xprt_complete_rqst(req->rq_task, svsk->sk_reclen);
 	rqstp->rq_arg.len = 0;
+	spin_unlock_bh(&bc_xprt->transport_lock);
 	return 0;
+unlock_notfound:
+	printk(KERN_NOTICE
+		"%s: Got unrecognized reply: "
+		"calldir 0x%x xpt_bc_xprt %p xid %08x\n",
+		__func__, ntohl(calldir),
+		bc_xprt, ntohl(xid));
+unlock_eagain:
+	spin_unlock_bh(&bc_xprt->transport_lock);
+	return -EAGAIN;
 }
 
 static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)
-- 
1.9.1

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