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authorMohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>2017-04-27 12:45:38 +0530
committerJohannes Berg <johannes.berg@intel.com>2017-04-28 12:28:44 +0200
commit21a8e9dd52b64f0170bad208293ef8c30c3c1403 (patch)
treeaf61429b6f3d3f06f3c1a47690aa31dbcff23ee3 /net/mac80211/tx.c
parent5fe49a9d11644f4aa9034c7eedbcfc6e52373e10 (diff)
downloadlinux-21a8e9dd52b64f0170bad208293ef8c30c3c1403.tar.bz2
mac80211: Fix possible sband related NULL pointer de-reference
Existing API 'ieee80211_get_sdata_band' returns default 2 GHz band even if the channel context configuration is NULL. This crashes for chipsets which support 5 Ghz alone when it tries to access members of 'sband'. Channel context configuration can be NULL in multivif case and when channel switch is in progress (or) when it fails. Fix this by replacing the API 'ieee80211_get_sdata_band' with 'ieee80211_get_sband' which returns a NULL pointer for sband when the channel configuration is NULL. An example scenario is as below: In multivif mode (AP + STA) with drivers like ath10k, when we do a channel switch in the AP vif (which has a number of clients connected) and a STA vif which is connected to some other AP, when the channel switch in AP vif fails, while the STA vifs tries to connect to the other AP, there is a window where the channel context is NULL/invalid and this results in a crash while the clients connected to the AP vif tries to reconnect and this race is very similar to the one investigated by Michal in https://patchwork.kernel.org/patch/3788161/ and this does happens with hardware that supports 5Ghz alone after long hours of testing with continuous channel switch on the AP vif ieee80211 phy0: channel context reservation cannot be finalized because some interfaces aren't switching wlan0: failed to finalize CSA, disconnecting wlan0-1: deauthenticating from 8c:fd:f0:01:54:9c by local choice (Reason: 3=DEAUTH_LEAVING) WARNING: CPU: 1 PID: 19032 at net/mac80211/ieee80211_i.h:1013 sta_info_alloc+0x374/0x3fc [mac80211] [<bf77272c>] (sta_info_alloc [mac80211]) [<bf78776c>] (ieee80211_add_station [mac80211])) [<bf73cc50>] (nl80211_new_station [cfg80211]) Unable to handle kernel NULL pointer dereference at virtual address 00000014 pgd = d5f4c000 Internal error: Oops: 17 [#1] PREEMPT SMP ARM PC is at sta_info_alloc+0x380/0x3fc [mac80211] LR is at sta_info_alloc+0x37c/0x3fc [mac80211] [<bf772738>] (sta_info_alloc [mac80211]) [<bf78776c>] (ieee80211_add_station [mac80211]) [<bf73cc50>] (nl80211_new_station [cfg80211])) Cc: Michal Kazior <michal.kazior@tieto.com> Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Diffstat (limited to 'net/mac80211/tx.c')
-rw-r--r--net/mac80211/tx.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index f27719eeeed7..04b22f8982fe 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -4297,7 +4297,10 @@ struct sk_buff *ieee80211_beacon_get_tim(struct ieee80211_hw *hw,
return bcn;
shift = ieee80211_vif_get_shift(vif);
- sband = hw->wiphy->bands[ieee80211_get_sdata_band(vif_to_sdata(vif))];
+ sband = ieee80211_get_sband(vif_to_sdata(vif));
+ if (!sband)
+ return bcn;
+
ieee80211_tx_monitor(hw_to_local(hw), copy, sband, 1, shift, false);
return bcn;