linux-kernel - [PATCH 4/4] sunrpc: lock xprt before trying to set memalloc on the sockets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1432987393-15604-5-git-send-email-jeff.layton@primarydata.com>
Date:	Sat, 30 May 2015 08:03:13 -0400
From:	Jeff Layton <jlayton@...chiereds.net>
To:	trond.myklebust@...marydata.com
Cc:	linux-nfs@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Jerome Marchand <jmarchan@...hat.com>
Subject: [PATCH 4/4] sunrpc: lock xprt before trying to set memalloc on the sockets

It's possible that we could race with a call to xs_reset_transport, in
which case the xprt->inet pointer could be zeroed out while we're
accessing it. Lock the xprt before we try to set memalloc on it.

Cc: Mel Gorman <mgorman@...e.de>
Signed-off-by: Jeff Layton <jeff.layton@...marydata.com>
---
 net/sunrpc/xprtsock.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 359446442112..91770ccab608 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -1964,11 +1964,22 @@ static void xs_local_connect(struct rpc_xprt *xprt, struct rpc_task *task)
 }
 
 #ifdef CONFIG_SUNRPC_SWAP
+/*
+ * Note that this should be called with XPRT_LOCKED held (or when we otherwise
+ * know that we have exclusive access to the socket), to guard against
+ * races with xs_reset_transport.
+ */
 static void xs_set_memalloc(struct rpc_xprt *xprt)
 {
 	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
 			xprt);
 
+	/*
+	 * If there's no sock, then we have nothing to set. The
+	 * reconnecting process will get it for us.
+	 */
+	if (!transport->inet)
+		return;
 	if (atomic_read(&xprt->swapper))
 		sk_set_memalloc(transport->inet);
 }
@@ -1986,8 +1997,11 @@ xs_swapper_enable(struct rpc_xprt *xprt)
 	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
 			xprt);
 
+	if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE))
+		return -ERESTARTSYS;
 	if (atomic_inc_return(&xprt->swapper) == 1)
 		sk_set_memalloc(transport->inet);
+	xprt_release_xprt(xprt, NULL);
 	return 0;
 }
 
@@ -2004,8 +2018,11 @@ xs_swapper_disable(struct rpc_xprt *xprt)
 	struct sock_xprt *transport = container_of(xprt, struct sock_xprt,
 			xprt);
 
+	if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE))
+		return;
 	if (atomic_dec_and_test(&xprt->swapper))
 		sk_clear_memalloc(transport->inet);
+	xprt_release_xprt(xprt, NULL);
 }
 #else
 static void xs_set_memalloc(struct rpc_xprt *xprt)
-- 
2.4.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/