linux-kernel - [PATCH 3.2 088/115] bridge: Only call /sbin/bridge-stp for the initial network namespace

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Message-ID: <lsq.1461711744.857844093@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:24 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Hannes Frederic Sowa" <hannes@...essinduktion.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.2 088/115] bridge: Only call /sbin/bridge-stp for the
 initial  network namespace

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

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

From: Hannes Frederic Sowa <hannes@...essinduktion.org>

[ Upstream commit ff62198553e43cdffa9d539f6165d3e83f8a42bc ]

[I stole this patch from Eric Biederman. He wrote:]

> There is no defined mechanism to pass network namespace information
> into /sbin/bridge-stp therefore don't even try to invoke it except
> for bridge devices in the initial network namespace.
>
> It is possible for unprivileged users to cause /sbin/bridge-stp to be
> invoked for any network device name which if /sbin/bridge-stp does not
> guard against unreasonable arguments or being invoked twice on the
> same network device could cause problems.

[Hannes: changed patch using netns_eq]

Cc: Eric W. Biederman <ebiederm@...ssion.com>
Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/bridge/br_stp_if.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -129,7 +129,10 @@ static void br_stp_start(struct net_brid
 	char *argv[] = { BR_STP_PROG, br->dev->name, "start", NULL };
 	char *envp[] = { NULL };
 
-	r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
+	if (net_eq(dev_net(br->dev), &init_net))
+		r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
+	else
+		r = -ENOENT;
 	if (r == 0) {
 		br->stp_enabled = BR_USER_STP;
 		br_debug(br, "userspace STP started\n");