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 modules then triggers
a use-after-free:

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

Use-after-free read at 0x00000000967e0109 (in kfence-torvalds#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-torvalds#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 saving the filename in pdata->tplg_filename instead, just like
every other code path that appends to the tplg filename.

Fixes: 5458411 ("ASoC: SOF: Intel: hda: refactoring topology name fixup for HDA mach")
Signed-off-by: Tavian Barnes <[email protected]>

Author: tavianator

sound/soc/sof/intel/hda.c

@@ -1069,7 +1069,7 @@ static void hda_generic_machine_select(struct snd_sof_dev *sdev,
 				if (!tplg_filename)
 					return;
 
-				hda_mach->sof_tplg_filename = tplg_filename;
+				pdata->tplg_filename = tplg_filename;
 			}
 
 			if (codec_num == 2 ||