apparmor: fix uninitialized lsm_audit member

apparmor: fix uninitialized lsm_audit member

BugLink: http://bugs.launchpad.net/bugs/1268727
The task field in the lsm_audit struct needs to be initialized if
a change_hat fails, otherwise the following oops will occur

BUG: unable to handle kernel paging request at 0000002fbead7d08
IP: [<ffffffff8171153e>] _raw_spin_lock+0xe/0x50
PGD 1e3f35067 PUD 0
Oops: 0002 [#1] SMP
Modules linked in: pppox crc_ccitt p8023 p8022 psnap llc ax25 btrfs raid6_pq xor xfs libcrc32c dm_multipath scsi_dh kvm_amd dcdbas kvm microcode amd64_edac_mod joydev edac_core psmouse edac_mce_amd serio_raw k10temp sp5100_tco i2c_piix4 ipmi_si ipmi_msghandler acpi_power_meter mac_hid lp parport hid_generic usbhid hid pata_acpi mpt2sas ahci raid_class pata_atiixp bnx2 libahci scsi_transport_sas [last unloaded: tipc]
CPU: 2 PID: 699 Comm: changehat_twice Tainted: GF          O 3.13.0-7-generic #25-Ubuntu
Hardware name: Dell Inc. PowerEdge R415/08WNM9, BIOS 1.8.6 12/06/2011
task: ffff8802135c6000 ti: ffff880212986000 task.ti: ffff880212986000
RIP: 0010:[<ffffffff8171153e>]  [<ffffffff8171153e>] _raw_spin_lock+0xe/0x50
RSP: 0018:ffff880212987b68  EFLAGS: 00010006
RAX: 0000000000020000 RBX: 0000002fbead7500 RCX: 0000000000000000
RDX: 0000000000000292 RSI: ffff880212987ba8 RDI: 0000002fbead7d08
RBP: ffff880212987b68 R08: 0000000000000246 R09: ffff880216e572a0
R10: ffffffff815fd677 R11: ffffea0008469580 R12: ffffffff8130966f
R13: ffff880212987ba8 R14: 0000002fbead7d08 R15: ffff8800d8c6b830
FS:  00002b5e6c84e7c0(0000) GS:ffff880216e40000(0000) knlGS:0000000055731700
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000002fbead7d08 CR3: 000000021270f000 CR4: 00000000000006e0
Stack:
 ffff880212987b98 ffffffff81075f17 ffffffff8130966f 0000000000000009
 0000000000000000 0000000000000000 ffff880212987bd0 ffffffff81075f7c
 0000000000000292 ffff880212987c08 ffff8800d8c6b800 0000000000000026
Call Trace:
 [<ffffffff81075f17>] __lock_task_sighand+0x47/0x80
 [<ffffffff8130966f>] ? apparmor_cred_prepare+0x2f/0x50
 [<ffffffff81075f7c>] do_send_sig_info+0x2c/0x80
 [<ffffffff81075fee>] send_sig_info+0x1e/0x30
 [<ffffffff8130242d>] aa_audit+0x13d/0x190
 [<ffffffff8130c1dc>] aa_audit_file+0xbc/0x130
 [<ffffffff8130966f>] ? apparmor_cred_prepare+0x2f/0x50
 [<ffffffff81304cc2>] aa_change_hat+0x202/0x530
 [<ffffffff81308fc6>] aa_setprocattr_changehat+0x116/0x1d0
 [<ffffffff8130a11d>] apparmor_setprocattr+0x25d/0x300
 [<ffffffff812cee56>] security_setprocattr+0x16/0x20
 [<ffffffff8121fc87>] proc_pid_attr_write+0x107/0x130
 [<ffffffff811b7604>] vfs_write+0xb4/0x1f0
 [<ffffffff811b8039>] SyS_write+0x49/0xa0
 [<ffffffff8171a1bf>] tracesys+0xe1/0xe6

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>