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mac80211: fix race in ieee80211_register_hw()

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A race condition leading to a kernel crash is observed during invocation
of ieee80211_register_hw() on a dragonboard410c device having wcn36xx
driver built as a loadable module along with a wifi manager in user-space
waiting for a wifi device (wlanX) to be active.

Sequence diagram for a particular kernel crash scenario:

    user-space  ieee80211_register_hw()  ieee80211_tasklet_handler()
    ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       |                    |                 |
       |<---phy0----wiphy_register()          |
       |-----iwd if_add---->|                 |
       |                    |<---IRQ----(RX packet)
       |              Kernel crash            |
       |              due to unallocated      |
       |              workqueue.              |
       |                    |                 |
       |       alloc_ordered_workqueue()      |
       |                    |                 |
       |              Misc wiphy init.        |
       |                    |                 |
       |            ieee80211_if_add()        |
       |                    |                 |

As evident from above sequence diagram, this race condition isn't specific
to a particular wifi driver but rather the initialization sequence in
ieee80211_register_hw() needs to be fixed. So re-order the initialization
sequence and the updated sequence diagram would look like:

    user-space  ieee80211_register_hw()  ieee80211_tasklet_handler()
    ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
       |                    |                 |
       |       alloc_ordered_workqueue()      |
       |                    |                 |
       |              Misc wiphy init.        |
       |                    |                 |
       |<---phy0----wiphy_register()          |
       |-----iwd if_add---->|                 |
       |                    |<---IRQ----(RX packet)
       |                    |                 |
       |            ieee80211_if_add()        |
       |                    |                 |

Cc: stable@vger.kernel.org
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Link: https://lore.kernel.org/r/1586254255-28713-1-git-send-email-sumit.garg@linaro.org
[Johannes: fix rtnl imbalances]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Sumit Garg 2020-04-07 15:40:55 +05:30 committed by Johannes Berg
parent a710d21451
commit 52e04b4ce5
1 changed files with 13 additions and 11 deletions
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24
net/mac80211/main.c
View File

@ -1069,7 +1069,7 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
local->hw.wiphy->signal_type = CFG80211_SIGNAL_TYPE_UNSPEC;
if (hw->max_signal <= 0) {
result = -EINVAL;
goto fail_wiphy_register;
goto fail_workqueue;
}
}
@ -1135,7 +1135,7 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
result = ieee80211_init_cipher_suites(local);
if (result < 0)
goto fail_wiphy_register;
goto fail_workqueue;
if (!local->ops->remain_on_channel)
local->hw.wiphy->max_remain_on_channel_duration = 5000;
@ -1161,10 +1161,6 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
local->hw.wiphy->max_num_csa_counters = IEEE80211_MAX_CSA_COUNTERS_NUM;
result = wiphy_register(local->hw.wiphy);
if (result < 0)
goto fail_wiphy_register;
/*
* We use the number of queues for feature tests (QoS, HT) internally
* so restrict them appropriately.
@ -1217,9 +1213,9 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
goto fail_flows;
rtnl_lock();
result = ieee80211_init_rate_ctrl_alg(local,
hw->rate_control_algorithm);
rtnl_unlock();
if (result < 0) {
wiphy_debug(local->hw.wiphy,
"Failed to initialize rate control algorithm\n");
@ -1273,6 +1269,12 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
local->sband_allocated |= BIT(band);
}
result = wiphy_register(local->hw.wiphy);
if (result < 0)
goto fail_wiphy_register;
rtnl_lock();
/* add one default STA interface if supported */
if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_STATION) &&
!ieee80211_hw_check(hw, NO_AUTO_VIF)) {
@ -1312,17 +1314,17 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
#if defined(CONFIG_INET) || defined(CONFIG_IPV6)
fail_ifa:
#endif
wiphy_unregister(local->hw.wiphy);
fail_wiphy_register:
rtnl_lock();
rate_control_deinitialize(local);
ieee80211_remove_interfaces(local);
fail_rate:
rtnl_unlock();
fail_rate:
fail_flows:
ieee80211_led_exit(local);
destroy_workqueue(local->workqueue);
fail_workqueue:
wiphy_unregister(local->hw.wiphy);
fail_wiphy_register:
if (local->wiphy_ciphers_allocated)
kfree(local->hw.wiphy->cipher_suites);
kfree(local->int_scan_req);
@ -1372,8 +1374,8 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)
skb_queue_purge(&local->skb_queue_unreliable);
skb_queue_purge(&local->skb_queue_tdls_chsw);
destroy_workqueue(local->workqueue);
wiphy_unregister(local->hw.wiphy);
destroy_workqueue(local->workqueue);
ieee80211_led_exit(local);
kfree(local->int_scan_req);
}