linux-kernel - [PATCH 3.16 252/305] SUNRPC: Fix a potential race in xprt

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: <lsq.1549201508.685829924@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Trond Myklebust" <trond.myklebust@...merspace.com>
Subject: [PATCH 3.16 252/305] SUNRPC: Fix a potential race in xprt_connect()

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

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

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

commit 0a9a4304f3614e25d9de9b63502ca633c01c0d70 upstream.

If an asynchronous connection attempt completes while another task is
in xprt_connect(), then the call to rpc_sleep_on() could end up
racing with the call to xprt_wake_pending_tasks().
So add a second test of the connection state after we've put the
task to sleep and set the XPRT_CONNECTING flag, when we know that there
can be no asynchronous connection attempts still in progress.

Fixes: 0b9e79431377d ("SUNRPC: Move the test for XPRT_CONNECTING into...")
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/sunrpc/xprt.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -721,8 +721,15 @@ void xprt_connect(struct rpc_task *task)
 			return;
 		if (xprt_test_and_set_connecting(xprt))
 			return;
-		xprt->stat.connect_start = jiffies;
-		xprt->ops->connect(xprt, task);
+		/* Race breaker */
+		if (!xprt_connected(xprt)) {
+			xprt->stat.connect_start = jiffies;
+			xprt->ops->connect(xprt, task);
+		} else {
+			xprt_clear_connecting(xprt);
+			task->tk_status = 0;
+			rpc_wake_up_queued_task(&xprt->pending, task);
+		}
 	}
 }