ASoC: SOF: Intel: hda: Fix UAF when reloading module

hda_generic_machine_select() appends -idisp to the tplg filename by
allocating a new string with devm_kasprintf(), then stores the string
right back into the global variable snd_soc_acpi_intel_hda_machines.
When the module is unloaded, this memory is freed, resulting in a global
variable pointing to freed memory.  Reloading the module then triggers
a use-after-free:

BUG: KFENCE: use-after-free read in string+0x48/0xe0

Use-after-free read at 0x00000000967e0109 (in kfence-kernel-patches#99):
 string+0x48/0xe0
 vsnprintf+0x329/0x6e0
 devm_kvasprintf+0x54/0xb0
 devm_kasprintf+0x58/0x80
 hda_machine_select.cold+0x198/0x17a2 [snd_sof_intel_hda_generic]
 sof_probe_work+0x7f/0x600 [snd_sof]
 process_one_work+0x17b/0x330
 worker_thread+0x2ce/0x3f0
 kthread+0xcf/0x100
 ret_from_fork+0x31/0x50
 ret_from_fork_asm+0x1a/0x30

kfence-kernel-patches#99: 0x00000000198a940f-0x00000000ace47d9d, size=64, cache=kmalloc-64

allocated by task 333 on cpu 8 at 17.798069s (130.453553s ago):
 devm_kmalloc+0x52/0x120
 devm_kvasprintf+0x66/0xb0
 devm_kasprintf+0x58/0x80
 hda_machine_select.cold+0x198/0x17a2 [snd_sof_intel_hda_generic]
 sof_probe_work+0x7f/0x600 [snd_sof]
 process_one_work+0x17b/0x330
 worker_thread+0x2ce/0x3f0
 kthread+0xcf/0x100
 ret_from_fork+0x31/0x50
 ret_from_fork_asm+0x1a/0x30

freed by task 1543 on cpu 4 at 141.586686s (6.665010s ago):
 release_nodes+0x43/0xb0
 devres_release_all+0x90/0xf0
 device_unbind_cleanup+0xe/0x70
 device_release_driver_internal+0x1c1/0x200
 driver_detach+0x48/0x90
 bus_remove_driver+0x6d/0xf0
 pci_unregister_driver+0x42/0xb0
 __do_sys_delete_module+0x1d1/0x310
 do_syscall_64+0x82/0x190
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Fix it by copying the match array with devm_kmemdup_array() before we
modify it.

Fixes: 5458411 ("ASoC: SOF: Intel: hda: refactoring topology name fixup for HDA mach")
Suggested-by: Peter Ujfalusi <[email protected]>
Acked-by: Peter Ujfalusi <[email protected]>
Signed-off-by: Tavian Barnes <[email protected]>
Link: https://patch.msgid.link/570b15570b274520a0d9052f4e0f064a29c950ef.1747229716.git.tavianator@tavianator.com
Signed-off-by: Mark Brown <[email protected]>

Author: tavianator

sound/soc/sof/intel/hda.c

@@ -1049,7 +1049,21 @@ static void hda_generic_machine_select(struct snd_sof_dev *sdev,
 		if (!*mach && codec_num <= 2) {
 			bool tplg_fixup = false;
 
-			hda_mach = snd_soc_acpi_intel_hda_machines;
+			/*
+			 * make a local copy of the match array since we might
+			 * be modifying it
+			 */
+			hda_mach = devm_kmemdup_array(sdev->dev,
+					snd_soc_acpi_intel_hda_machines,
+					2, /* we have one entry + sentinel in the array */
+					sizeof(snd_soc_acpi_intel_hda_machines[0]),
+					GFP_KERNEL);
+			if (!hda_mach) {
+				dev_err(bus->dev,
+					"%s: failed to duplicate the HDA match table\n",
+					__func__);
+				return;
+			}
 
 			dev_info(bus->dev, "using HDA machine driver %s now\n",
 				 hda_mach->drv_name);