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    Subject[PATCH 3.16 205/254] nl80211: take RCU read lock when calling ieee80211_bss_get_ie()
    3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

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

    From: Dominik Brodowski <linux@dominikbrodowski.net>

    commit 7a94b8c2eee7083ddccd0515830f8c81a8e44b1a upstream.

    As ieee80211_bss_get_ie() derefences an RCU to return ssid_ie, both
    the call to this function and any operation on this variable need
    protection by the RCU read lock.

    Fixes: 44905265bc15 ("nl80211: don't expose wdev->ssid for most interfaces")
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    net/wireless/nl80211.c | 11 +++++++----
    1 file changed, 7 insertions(+), 4 deletions(-)

    --- a/net/wireless/nl80211.c
    +++ b/net/wireless/nl80211.c
    @@ -2354,12 +2354,13 @@ static int nl80211_send_iface(struct sk_
    const u8 *ssid_ie;
    if (!wdev->current_bss)
    break;
    + rcu_read_lock();
    ssid_ie = ieee80211_bss_get_ie(&wdev->current_bss->pub,
    WLAN_EID_SSID);
    - if (!ssid_ie)
    - break;
    - if (nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
    - goto nla_put_failure_locked;
    + if (ssid_ie &&
    + nla_put(msg, NL80211_ATTR_SSID, ssid_ie[1], ssid_ie + 2))
    + goto nla_put_failure_rcu_locked;
    + rcu_read_unlock();
    break;
    }
    default:
    @@ -2370,6 +2371,8 @@ static int nl80211_send_iface(struct sk_

    return genlmsg_end(msg, hdr);

    + nla_put_failure_rcu_locked:
    + rcu_read_unlock();
    nla_put_failure_locked:
    wdev_unlock(wdev);
    nla_put_failure:
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