linux-kernel - [PATCH] platform/x86/intel: Fix 'rmmod pmt

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Message-Id: <20220429122322.2550003-1-prarit@redhat.com>
Date:   Fri, 29 Apr 2022 08:23:22 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Prarit Bhargava <prarit@...hat.com>,
        "David E. Box" <david.e.box@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        platform-driver-x86@...r.kernel.org,
        David Arcari <darcari@...hat.com>
Subject: [PATCH] platform/x86/intel: Fix 'rmmod pmt_telemetry' panic

'rmmod pmt_telemetry' panics with:

 BUG: kernel NULL pointer dereference, address: 0000000000000040
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 4 PID: 1697 Comm: rmmod Tainted: G S      W        --------  ---  5.18.0-rc4 #3
 Hardware name: Intel Corporation Alder Lake Client Platform/AlderLake-P DDR5 RVP, BIOS ADLPFWI1.R00.3056.B00.2201310233 01/31/2022
 RIP: 0010:device_del+0x1b/0x3d0
 Code: e8 1a d9 e9 ff e9 58 ff ff ff 48 8b 08 eb dc 0f 1f 44 00 00 41 56 41 55 41 54 55 48 8d af 80 00 00 00 53 48 89 fb 48 83 ec 18 <4c> 8b 67 40 48 89 ef 65 48 8b 04 25 28 00 00 00 48 89 44 24 10 31
 RSP: 0018:ffffb520415cfd60 EFLAGS: 00010286
 RAX: 0000000000000070 RBX: 0000000000000000 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: 0000000000000080 R08: ffffffffffffffff R09: ffffb520415cfd78
 R10: 0000000000000002 R11: ffffb520415cfd78 R12: 0000000000000000
 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 FS:  00007f7e198e5740(0000) GS:ffff905c9f700000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000040 CR3: 000000010782a005 CR4: 0000000000770ee0
 PKRU: 55555554
 Call Trace:
  <TASK>
  ? __xa_erase+0x53/0xb0
  device_unregister+0x13/0x50
  intel_pmt_dev_destroy+0x34/0x60 [pmt_class]
  pmt_telem_remove+0x40/0x50 [pmt_telemetry]
  auxiliary_bus_remove+0x18/0x30
  device_release_driver_internal+0xc1/0x150
  driver_detach+0x44/0x90
  bus_remove_driver+0x74/0xd0
  auxiliary_driver_unregister+0x12/0x20
  pmt_telem_exit+0xc/0xe4a [pmt_telemetry]
  __x64_sys_delete_module+0x13a/0x250
  ? syscall_trace_enter.isra.19+0x11e/0x1a0
  do_syscall_64+0x58/0x80
  ? syscall_exit_to_user_mode+0x12/0x30
  ? do_syscall_64+0x67/0x80
  ? syscall_exit_to_user_mode+0x12/0x30
  ? do_syscall_64+0x67/0x80
  ? syscall_exit_to_user_mode+0x12/0x30
  ? do_syscall_64+0x67/0x80
  ? exc_page_fault+0x64/0x140
  entry_SYSCALL_64_after_hwframe+0x44/0xae
 RIP: 0033:0x7f7e1803a05b
 Code: 73 01 c3 48 8b 0d 2d 4e 38 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d fd 4d 38 00 f7 d8 64 89 01 48

The probe function, pmt_telem_probe(), adds an entry for devices even if
they have not been initialized.  This results in the array of initialized
devices containing both initialized and uninitialized entries.  This
causes a panic in the remove function, pmt_telem_remove() which expects
the array to only contain initialized entries.

Only use an entry when a device is initialized.

Cc: "David E. Box" <david.e.box@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>
Cc: Mark Gross <markgross@...nel.org>
Cc: platform-driver-x86@...r.kernel.org
Signed-off-by: David Arcari <darcari@...hat.com>
Signed-off-by: Prarit Bhargava <prarit@...hat.com>
---
 drivers/platform/x86/intel/pmt/telemetry.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/intel/pmt/telemetry.c b/drivers/platform/x86/intel/pmt/telemetry.c
index 6b6f3e2a617a..f73ecfd4a309 100644
--- a/drivers/platform/x86/intel/pmt/telemetry.c
+++ b/drivers/platform/x86/intel/pmt/telemetry.c
@@ -103,7 +103,7 @@ static int pmt_telem_probe(struct auxiliary_device *auxdev, const struct auxilia
 	auxiliary_set_drvdata(auxdev, priv);
 
 	for (i = 0; i < intel_vsec_dev->num_resources; i++) {
-		struct intel_pmt_entry *entry = &priv->entry[i];
+		struct intel_pmt_entry *entry = &priv->entry[priv->num_entries];
 
 		ret = intel_pmt_dev_create(entry, &pmt_telem_ns, intel_vsec_dev, i);
 		if (ret < 0)
-- 
2.35.1