linux-kernel - [PATCH 4.19 128/168] svcrdma: Fix page leak in svc_rdma_recv_read

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Message-Id: <20200817143740.079593346@linuxfoundation.org>
Date:   Mon, 17 Aug 2020 17:17:39 +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>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 128/168] svcrdma: Fix page leak in svc_rdma_recv_read_chunk()

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

[ Upstream commit e814eecbe3bbeaa8b004d25a4b8974d232b765a9 ]

Commit 07d0ff3b0cd2 ("svcrdma: Clean up Read chunk path") moved the
page saver logic so that it gets executed event when an error occurs.
In that case, the I/O is never posted, and those pages are then
leaked. Errors in this path, however, are quite rare.

Fixes: 07d0ff3b0cd2 ("svcrdma: Clean up Read chunk path")
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sunrpc/xprtrdma/svc_rdma_rw.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 4fc0ce1270894..22f1352638151 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -679,7 +679,6 @@ static int svc_rdma_build_read_chunk(struct svc_rqst *rqstp,
 				     struct svc_rdma_read_info *info,
 				     __be32 *p)
 {
-	unsigned int i;
 	int ret;
 
 	ret = -EINVAL;
@@ -702,12 +701,6 @@ static int svc_rdma_build_read_chunk(struct svc_rqst *rqstp,
 		info->ri_chunklen += rs_length;
 	}
 
-	/* Pages under I/O have been copied to head->rc_pages.
-	 * Prevent their premature release by svc_xprt_release() .
-	 */
-	for (i = 0; i < info->ri_readctxt->rc_page_count; i++)
-		rqstp->rq_pages[i] = NULL;
-
 	return ret;
 }
 
@@ -802,6 +795,26 @@ static int svc_rdma_build_pz_read_chunk(struct svc_rqst *rqstp,
 	return ret;
 }
 
+/* Pages under I/O have been copied to head->rc_pages. Ensure they
+ * are not released by svc_xprt_release() until the I/O is complete.
+ *
+ * This has to be done after all Read WRs are constructed to properly
+ * handle a page that is part of I/O on behalf of two different RDMA
+ * segments.
+ *
+ * Do this only if I/O has been posted. Otherwise, we do indeed want
+ * svc_xprt_release() to clean things up properly.
+ */
+static void svc_rdma_save_io_pages(struct svc_rqst *rqstp,
+				   const unsigned int start,
+				   const unsigned int num_pages)
+{
+	unsigned int i;
+
+	for (i = start; i < num_pages + start; i++)
+		rqstp->rq_pages[i] = NULL;
+}
+
 /**
  * svc_rdma_recv_read_chunk - Pull a Read chunk from the client
  * @rdma: controlling RDMA transport
@@ -855,6 +868,7 @@ int svc_rdma_recv_read_chunk(struct svcxprt_rdma *rdma, struct svc_rqst *rqstp,
 	ret = svc_rdma_post_chunk_ctxt(&info->ri_cc);
 	if (ret < 0)
 		goto out_err;
+	svc_rdma_save_io_pages(rqstp, 0, head->rc_page_count);
 	return 0;
 
 out_err:
-- 
2.25.1