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bridge: Clamp forward_delay when enabling STP
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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>
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Herbert Xu authored and David S. Miller committed Sep 13, 2013
1 parent 9a06201 commit be4f154
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Showing 3 changed files with 26 additions and 8 deletions.
1 change: 1 addition & 0 deletions net/bridge/br_private.h
Original file line number Diff line number Diff line change
Expand Up @@ -746,6 +746,7 @@ 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);
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21 changes: 15 additions & 6 deletions net/bridge/br_stp.c
Original file line number Diff line number Diff line change
Expand Up @@ -544,18 +544,27 @@ 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;
}
12 changes: 10 additions & 2 deletions net/bridge/br_stp_if.c
Original file line number Diff line number Diff line change
Expand Up @@ -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");
Expand All @@ -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)
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