[PATCH] PCI: fix use-after-free in pci_pme_list_scan()

[Torsten Hilbrich <torsten.hilbrich@secunet.com>]

struct pci_pme_device holds a raw, non-refcounted pointer to the
pci_dev it tracks. A device is added to pci_pme_list by pci_pme_active()
only while its pme_poll flag is set, but that flag can be cleared by the
various PME wakeup paths (pci_acpi_wake_dev(), pcie_pme_handle_request(),
pcie_pme_walk_bus(), pci_pme_wakeup()) without removing the entry from the
list.

On device teardown, pci_stop_dev() -> pci_pme_active(dev, false) skips
the list removal whenever pme_poll has already been cleared, so the entry
is left behind. pci_destroy_dev() then frees the pci_dev while its entry
is still on the list, and the periodic pci_pme_list_scan() work
dereferences the freed structure, causing a use-after-free (observed as a
general protection fault on a PaX 0xfe-poisoned pointer).

Take a reference to the pci_dev for each list entry (pci_dev_get() when
adding) and drop it when the entry is removed, both in pci_pme_list_scan()
and in pci_pme_active(). This keeps the device alive as long as its entry
is on the list, regardless of the pme_poll state or teardown ordering.

Patch is based on v7.3-rc1.

The problem was found when using PaX memory free poisoning (0xfe). Here
is the panic from a v6.18.45 test run. It happened after disconnecting
a TB4 dock with 2 displays connected.

<6>[66245.416348] usb 5-1.4.4.4: USB disconnect, device number 19
<6>[66245.448107] [drm] drm_dp_dpcd_access card0-DP-4 via AMDGPU DM aux hw bus 5: Too many retries, giving up. First error: -5, First reply: 0x0, Last reply: 0x0, Request: 0x9, Address: 0x111, Size: 0x1
<6>[66245.485882] [drm] drm_dp_dpcd_access card0-DP-4 via AMDGPU DM aux hw bus 5: Too many retries, giving up. First error: -5, First reply: 0x0, Last reply: 0x0, Request: 0x8, Address: 0x111, Size: 0x1
<4>[66245.930686] Oops: general protection fault, probably for non-canonical address 0xfefefefefefeff36: 0000 [#1] SMP NOPTI
<4>[66245.931209] CPU: 0 UID: 0 PID: 21940 Comm: kworker/0:4 Tainted: P           O        6.18.45-grsec+ #1 PREEMPT(voluntary) 
<4>[66245.931623] Tainted: [P]=PROPRIETARY_MODULE, [O]=OOT_MODULE
<4>[66245.931890] Hardware name: LENOVO 21QKS01V00/21QKS01V00, BIOS R2XET42T (1.21 ) 08/20/2026
<4>[66245.932213] Workqueue: events_freezable pci_pme_list_scan
<4>[66245.932475] RIP: 0010:[<ffffffff818f09ec>] pci_pme_list_scan+0x4c/0x1f0
<4>[66245.932761] Code: 1f 03 4c 8b 23 48 89 df 48 81 fb c0 64 ae 84 0f 84 36 01 00 00 48 8b 6b 10 f6 85 9d 00 00 00 20 0f 84 88 00 00 00 48 8b 45 10 <48> 8b 58 38 48 85 db 0f 84 b2 00 00 00 49 89 de 49 81 c6 c0 00 00
<4>[66245.933346] RSP: 0018:ffffc9002109bee8 EFLAGS: 00010202
<4>[66245.933607] RAX: fefefefefefefefe RBX: ffff8901040c10e0 RCX: ffff8907dca25828
<4>[66245.933916] RDX: ffff890181762940 RSI: 0000000000000000 RDI: ffff8901040c10e0
<4>[66245.934227] RBP: ffff8905fe998000 R08: ffffffffffffffff R09: ffff89010000d4c0
<4>[66245.934538] R10: ffff89046b63ff40 R11: fefefefefefefeff R12: ffff8901040c1a60
<4>[66245.934848] R13: ffff8907dca25800 R14: ffff8901000a3205 R15: 0000000000000000
<4>[66245.935172] RBX: kmalloc-32+0x0/0x20 [slab object]
<4>[66245.935433] RCX: cpu_worker_pools+0x28/0x640 [percpu0 25828]
<4>[66245.935718] RDX: task_struct[kworker/0:4+events_freezable 21940 21940]+0x0/0xdc0 [slab object]
<4>[66245.936076] RDI: kmalloc-32+0x0/0x20 [slab object]
<4>[66245.936339] RBP: kmalloc-4k+0x0/0x1000 [slab object]
<4>[66245.936609] RSP: vm[ffffc90021098000 4002 kernel_clone+0xcc/0x450]+0x3ee8/0x4000 [vmalloc]
<4>[66245.936958] R08: -EPERM
<4>[66245.937166] R09: kmalloc-512+0xc0/0x200 [slab object]
<4>[66245.937437] R10: kmalloc-192+0x80/0xc0 [slab object]
<4>[66245.937706] R12: kmalloc-32+0x0/0x20 [slab object]
<4>[66245.937972] R13: cpu_worker_pools+0x0/0x640 [percpu0 25800]
<4>[66245.938261] R14: pool_workqueue+0x5/0x200 [slab object]
<4>[66245.938542] FS:  0000000000000000(0000) GS:ffff890856bdd000(0000) knlGS:0000000000000000
<4>[66245.938893] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[66245.939187] CR2: ffff9a8a2c97d000 CR3: 0000000182794000 CR4: 0000000000740ef0 shadow CR4: 0000000000740ef0
<4>[66245.939581] PKRU: 55555554
<4>[66245.939807] Stack:
<4>[66245.940015]  ffff89046b63fec0 ffffffff84ae6440 ffff8901000a3200 ffff8907dca25800
<4>[66245.940355]  ffff8901000a3205 ffffffff812f497a ffff8907dca25800 ffff89046b63ff00
<4>[66245.940697]  ffff8907dca25828 ffff89046b63fec0 ffff8907dca25800 0000000000000000
<4>[66245.941045] Call Trace:
<4>[66245.941269]  <TASK>
<4>[66245.941484]  [<ffffffff812f497a>] process_one_work+0x1ca/0x4b0 ffffc9002109bf10
<4>[66245.941829]  [<ffffffff812f569c>] worker_thread+0x16c/0x2f0 ffffc9002109bf48
<4>[66245.942165]  [<ffffffff812f5530>] ? __pfx_worker_thread+0x10/0x10 ffffc9002109bf68
<4>[66245.942513]  [<ffffffff812fe89f>] kthread+0x12f/0x270 ffffc9002109bf80
<4>[66245.942837]  [<ffffffff812fe770>] ? __pfx_kthread+0x10/0x10 ffffc9002109bf88
<4>[66245.943174]  [<ffffffff812fe770>] ? __pfx_kthread+0x10/0x10 ffffc9002109bf98
<4>[66245.943508]  [<ffffffff81265203>] ret_from_fork+0x173/0x190 ffffc9002109bfc8
<4>[66245.943842]  [<ffffffff812fe770>] ? __pfx_kthread+0x10/0x10 ffffc9002109bfd0
<4>[66245.944175]  [<ffffffff81221639>] ret_from_fork_asm+0x29/0x50 ffffc9002109bfe8
<4>[66245.944512]  </TASK>
<4>[66245.944727] Modules linked in: vtx(O) vboxdrv(O) pl2303 ftdi_sio usbserial modstop_test_unload(O) mcd_drv(O) wacom mac_passthrough(O) dm_crypt_sina(O) chiasmus(PO) cryptoapi_plugger(O) dm_mod
<4>[66245.945340] ---[ end trace 0000000000000000 ]---

Assisted-by: LLM opencode
Signed-off-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
---
 drivers/pci/pci.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b2879a6be5f80..b3a4b710d7c8d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2410,6 +2410,7 @@ static void pci_pme_list_scan(struct work_struct *work)
 				pm_runtime_put(bdev);
 		} else {
 			list_del(&pme_dev->list);
+			pci_dev_put(pdev);
 			kfree(pme_dev);
 		}
 	}
@@ -2497,7 +2498,7 @@ void pci_pme_active(struct pci_dev *dev, bool enable)
 				pci_warn(dev, "can't enable PME#\n");
 				return;
 			}
-			pme_dev->dev = dev;
+			pme_dev->dev = pci_dev_get(dev);
 			mutex_lock(&pci_pme_list_mutex);
 			list_add(&pme_dev->list, &pci_pme_list);
 			if (list_is_singular(&pci_pme_list))
@@ -2510,6 +2511,7 @@ void pci_pme_active(struct pci_dev *dev, bool enable)
 			list_for_each_entry(pme_dev, &pci_pme_list, list) {
 				if (pme_dev->dev == dev) {
 					list_del(&pme_dev->list);
+					pci_dev_put(pme_dev->dev);
 					kfree(pme_dev);
 					break;
 				}
-- 
2.47.3