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    Subject[ 022/110] bridge: Clamp forward_delay when enabling STP
    Date
    3.10-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>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    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(-)

    --- a/net/bridge/br_private.h
    +++ b/net/bridge/br_private.h
    @@ -714,6 +714,7 @@ extern struct net_bridge_port *br_get_po
    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);
    --- a/net/bridge/br_stp.c
    +++ b/net/bridge/br_stp.c
    @@ -544,18 +544,27 @@ int br_set_max_age(struct net_bridge *br

    }

    +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;
    }
    --- 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_brid
    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_brid
    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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