[PATCH] platform/x86: asus-wmi: Fix NULL pointer dereference

["João Paulo Rechi Vita" <jprvita@gmail.com>]

Do not perform the rfkill cleanup routine when
(asus->driver->wlan_ctrl_by_user && ashs_present()) is true, since
nothing is registered with the rfkill subsystem in that case. Doing so
leads to the following kernel NULL pointer dereference:

  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: [<ffffffff816c7348>] __mutex_lock_slowpath+0x98/0x120
  PGD 1a3aa8067
  PUD 1a3b3d067
  PMD 0

  Oops: 0002 [#1] PREEMPT SMP
  Modules linked in: bnep ccm binfmt_misc uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core hid_a4tech videodev x86_pkg_temp_thermal intel_powerclamp coretemp ath3k btusb btrtl btintel bluetooth kvm_intel snd_hda_codec_hdmi kvm snd_hda_codec_realtek snd_hda_codec_generic irqbypass crc32c_intel arc4 i915 snd_hda_intel snd_hda_codec ath9k ath9k_common ath9k_hw ath i2c_algo_bit snd_hwdep mac80211 ghash_clmulni_intel snd_hda_core snd_pcm snd_timer cfg80211 ehci_pci xhci_pci drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm xhci_hcd ehci_hcd asus_nb_wmi(-) asus_wmi sparse_keymap r8169 rfkill mxm_wmi serio_raw snd mii mei_me lpc_ich i2c_i801 video soundcore mei i2c_smbus wmi i2c_core mfd_core
  CPU: 3 PID: 3275 Comm: modprobe Not tainted 4.9.34-gentoo #34
  Hardware name: ASUSTeK COMPUTER INC. K56CM/K56CM, BIOS K56CM.206 08/21/2012
  task: ffff8801a639ba00 task.stack: ffffc900014cc000
  RIP: 0010:[<ffffffff816c7348>]  [<ffffffff816c7348>] __mutex_lock_slowpath+0x98/0x120
  RSP: 0018:ffffc900014cfce0  EFLAGS: 00010282
  RAX: 0000000000000000 RBX: ffff8801a54315b0 RCX: 00000000c0000100
  RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff8801a54315b4
  RBP: ffffc900014cfd30 R08: 0000000000000000 R09: 0000000000000002
  R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801a54315b4
  R13: ffff8801a639ba00 R14: 00000000ffffffff R15: ffff8801a54315b8
  FS:  00007faa254fb700(0000) GS:ffff8801aef80000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000000 CR3: 00000001a3b1b000 CR4: 00000000001406e0
  Stack:
   ffff8801a54315b8 0000000000000000 ffffffff814733ae ffffc900014cfd28
   ffffffff8146a28c ffff8801a54315b0 0000000000000000 ffff8801a54315b0
   ffff8801a66f3820 0000000000000000 ffffc900014cfd48 ffffffff816c73e7
  Call Trace:
   [<ffffffff814733ae>] ? acpi_ut_release_mutex+0x5d/0x61
   [<ffffffff8146a28c>] ? acpi_ns_get_node+0x49/0x52
   [<ffffffff816c73e7>] mutex_lock+0x17/0x30
   [<ffffffffa00a3bb4>] asus_rfkill_hotplug+0x24/0x1a0 [asus_wmi]
   [<ffffffffa00a4421>] asus_wmi_rfkill_exit+0x61/0x150 [asus_wmi]
   [<ffffffffa00a49f1>] asus_wmi_remove+0x61/0xb0 [asus_wmi]
   [<ffffffff814a5128>] platform_drv_remove+0x28/0x40
   [<ffffffff814a2901>] __device_release_driver+0xa1/0x160
   [<ffffffff814a29e3>] device_release_driver+0x23/0x30
   [<ffffffff814a1ffd>] bus_remove_device+0xfd/0x170
   [<ffffffff8149e5a9>] device_del+0x139/0x270
   [<ffffffff814a5028>] platform_device_del+0x28/0x90
   [<ffffffff814a50a2>] platform_device_unregister+0x12/0x30
   [<ffffffffa00a4209>] asus_wmi_unregister_driver+0x19/0x30 [asus_wmi]
   [<ffffffffa00da0ea>] asus_nb_wmi_exit+0x10/0xf26 [asus_nb_wmi]
   [<ffffffff8110c692>] SyS_delete_module+0x192/0x270
   [<ffffffff810022b2>] ? exit_to_usermode_loop+0x92/0xa0
   [<ffffffff816ca560>] entry_SYSCALL_64_fastpath+0x13/0x94
  Code: e8 5e 30 00 00 8b 03 83 f8 01 0f 84 93 00 00 00 48 8b 43 10 4c 8d 7b 08 48 89 63 10 41 be ff ff ff ff 4c 89 3c 24 48 89 44 24 08 <48> 89 20 4c 89 6c 24 10 eb 1d 4c 89 e7 49 c7 45 08 02 00 00 00
  RIP  [<ffffffff816c7348>] __mutex_lock_slowpath+0x98/0x120
   RSP <ffffc900014cfce0>
  CR2: 0000000000000000
  ---[ end trace 8d484233fa7cb512 ]---
  note: modprobe[3275] exited with preempt_count 2

https://bugzilla.kernel.org/show_bug.cgi?id=196467

Reported-by: red.f0xyz@gmail.com
Signed-off-by: João Paulo Rechi Vita <jprvita@endlessm.com>
---
 drivers/platform/x86/asus-wmi.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index ef87e78ca772..3d523ca64694 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -163,6 +163,16 @@ MODULE_LICENSE("GPL");
 
 static const char * const ashs_ids[] = { "ATK4001", "ATK4002", NULL };
 
+static bool ashs_present(void)
+{
+	int i = 0;
+	while (ashs_ids[i]) {
+		if (acpi_dev_found(ashs_ids[i++]))
+			return true;
+	}
+	return false;
+}
+
 struct bios_args {
 	u32 arg0;
 	u32 arg1;
@@ -1025,6 +1035,9 @@ static int asus_new_rfkill(struct asus_wmi *asus,
 
 static void asus_wmi_rfkill_exit(struct asus_wmi *asus)
 {
+	if (asus->driver->wlan_ctrl_by_user && ashs_present())
+		return;
+
 	asus_unregister_rfkill_notifier(asus, "\\_SB.PCI0.P0P5");
 	asus_unregister_rfkill_notifier(asus, "\\_SB.PCI0.P0P6");
 	asus_unregister_rfkill_notifier(asus, "\\_SB.PCI0.P0P7");
@@ -2120,16 +2133,6 @@ static int asus_wmi_fan_init(struct asus_wmi *asus)
 	return 0;
 }
 
-static bool ashs_present(void)
-{
-	int i = 0;
-	while (ashs_ids[i]) {
-		if (acpi_dev_found(ashs_ids[i++]))
-			return true;
-	}
-	return false;
-}
-
 /*
  * WMI Driver
  */
-- 
2.17.0