[ 3.8.y.z extended stable ] Patch "iwlwifi: dvm: fix calling ieee80211_chswitch_done() with NULL" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    iwlwifi: dvm: fix calling ieee80211_chswitch_done() with NULL

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From afb7963fd5895a45d84cadb978d3696cb1c772e5 Mon Sep 17 00:00:00 2001
From: Stanislaw Gruszka <sgruszka at redhat.com>
Date: Fri, 26 Jul 2013 15:29:09 +0200
Subject: iwlwifi: dvm: fix calling ieee80211_chswitch_done() with NULL

commit 9186a1fd9ed190739423db84bc344d258ef3e3d7 upstream.

If channel switch is pending and we remove interface we can
crash like showed below due to passing NULL vif to mac80211:

BUG: unable to handle kernel paging request at fffffffffffff8cc
IP: [<ffffffff8130924d>] strnlen+0xd/0x40
Call Trace:
 [<ffffffff8130ad2e>] string.isra.3+0x3e/0xd0
 [<ffffffff8130bf99>] vsnprintf+0x219/0x640
 [<ffffffff8130c481>] vscnprintf+0x11/0x30
 [<ffffffff81061585>] vprintk_emit+0x115/0x4f0
 [<ffffffff81657bd5>] printk+0x61/0x63
 [<ffffffffa048987f>] ieee80211_chswitch_done+0xaf/0xd0 [mac80211]
 [<ffffffffa04e7b34>] iwl_chswitch_done+0x34/0x40 [iwldvm]
 [<ffffffffa04f83c3>] iwlagn_commit_rxon+0x2a3/0xdc0 [iwldvm]
 [<ffffffffa04ebc50>] ? iwlagn_set_rxon_chain+0x180/0x2c0 [iwldvm]
 [<ffffffffa04e5e76>] iwl_set_mode+0x36/0x40 [iwldvm]
 [<ffffffffa04e5f0d>] iwlagn_mac_remove_interface+0x8d/0x1b0 [iwldvm]
 [<ffffffffa0459b3d>] ieee80211_do_stop+0x29d/0x7f0 [mac80211]

This is because we nulify ctx->vif in iwlagn_mac_remove_interface()
before calling some other functions that teardown interface. To fix
just check ctx->vif on iwl_chswitch_done(). We should not call
ieee80211_chswitch_done() as channel switch works were already canceled
by mac80211 in ieee80211_do_stop() -> ieee80211_mgd_stop().

Resolve:
https://bugzilla.redhat.com/show_bug.cgi?id=979581

Reported-by: Lukasz Jagiello <jagiello.lukasz at gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach at intel.com>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/wireless/iwlwifi/dvm/mac80211.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/iwlwifi/dvm/mac80211.c b/drivers/net/wireless/iwlwifi/dvm/mac80211.c
index c784f69..70c32db 100644
--- a/drivers/net/wireless/iwlwifi/dvm/mac80211.c
+++ b/drivers/net/wireless/iwlwifi/dvm/mac80211.c
@@ -961,7 +961,10 @@ void iwl_chswitch_done(struct iwl_priv *priv, bool is_success)
 	if (test_bit(STATUS_EXIT_PENDING, &priv->status))
 		return;

-	if (test_and_clear_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status))
+	if (!test_and_clear_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status))
+		return;
+
+	if (ctx->vif)
 		ieee80211_chswitch_done(ctx->vif, is_success);
 }

--
1.8.1.2