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Subject[PATCH 3.8 40/81] bridge: Clamp forward_delay when enabling STP
Date
3.8.13.12 -stable review patch.  If anyone has any objections, please let me know.

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

From: Herbert Xu <herbert@gondor.apana.org.au>

[ Upstream commit be4f154d5ef0ca147ab6bcd38857a774133f5450 ]

At some point limits were added to forward_delay. However, the
limits are only enforced when STP is enabled. This created a
scenario where you could have a value outside the allowed range
while STP is disabled, which then stuck around even after STP
is enabled.

This patch fixes this by clamping the value when we enable STP.

I had to move the locking around a bit to ensure that there is
no window where someone could insert a value outside the range
while we're in the middle of enabling STP.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Cheers,
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
net/bridge/br_private.h | 1 +
net/bridge/br_stp.c | 21 +++++++++++++++------
net/bridge/br_stp_if.c | 12 ++++++++++--
3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 711094a..e943215 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -552,6 +552,7 @@ extern struct net_bridge_port *br_get_port(struct net_bridge *br,
extern void br_init_port(struct net_bridge_port *p);
extern void br_become_designated_port(struct net_bridge_port *p);

+extern void __br_set_forward_delay(struct net_bridge *br, unsigned long t);
extern int br_set_forward_delay(struct net_bridge *br, unsigned long x);
extern int br_set_hello_time(struct net_bridge *br, unsigned long x);
extern int br_set_max_age(struct net_bridge *br, unsigned long x);
diff --git a/net/bridge/br_stp.c b/net/bridge/br_stp.c
index e26f712..26f4d73 100644
--- a/net/bridge/br_stp.c
+++ b/net/bridge/br_stp.c
@@ -537,18 +537,27 @@ int br_set_max_age(struct net_bridge *br, unsigned long val)

}

+void __br_set_forward_delay(struct net_bridge *br, unsigned long t)
+{
+ br->bridge_forward_delay = t;
+ if (br_is_root_bridge(br))
+ br->forward_delay = br->bridge_forward_delay;
+}
+
int br_set_forward_delay(struct net_bridge *br, unsigned long val)
{
unsigned long t = clock_t_to_jiffies(val);
+ int err = -ERANGE;

+ spin_lock_bh(&br->lock);
if (br->stp_enabled != BR_NO_STP &&
(t < BR_MIN_FORWARD_DELAY || t > BR_MAX_FORWARD_DELAY))
- return -ERANGE;
+ goto unlock;

- spin_lock_bh(&br->lock);
- br->bridge_forward_delay = t;
- if (br_is_root_bridge(br))
- br->forward_delay = br->bridge_forward_delay;
+ __br_set_forward_delay(br, t);
+ err = 0;
+
+unlock:
spin_unlock_bh(&br->lock);
- return 0;
+ return err;
}
diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 9d5a414..7ba2ed5 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -129,6 +129,14 @@ static void br_stp_start(struct net_bridge *br)
char *envp[] = { NULL };

r = call_usermodehelper(BR_STP_PROG, argv, envp, UMH_WAIT_PROC);
+
+ spin_lock_bh(&br->lock);
+
+ if (br->bridge_forward_delay < BR_MIN_FORWARD_DELAY)
+ __br_set_forward_delay(br, BR_MIN_FORWARD_DELAY);
+ else if (br->bridge_forward_delay < BR_MAX_FORWARD_DELAY)
+ __br_set_forward_delay(br, BR_MAX_FORWARD_DELAY);
+
if (r == 0) {
br->stp_enabled = BR_USER_STP;
br_debug(br, "userspace STP started\n");
@@ -137,10 +145,10 @@ static void br_stp_start(struct net_bridge *br)
br_debug(br, "using kernel STP\n");

/* To start timers on any ports left in blocking */
- spin_lock_bh(&br->lock);
br_port_state_selection(br);
- spin_unlock_bh(&br->lock);
}
+
+ spin_unlock_bh(&br->lock);
}

static void br_stp_stop(struct net_bridge *br)
--
1.8.1.2


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