Re: [PATCH v4] ASoC: SOF: Intel: hda: Fix UAF when reloading module

["Péter Ujfalusi" <peter.ujfalusi@linux.intel.com>]

On 08/05/2025 18:21, Tavian Barnes wrote:
> 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-#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-#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: 5458411d7594 ("ASoC: SOF: Intel: hda: refactoring topology name fixup for HDA mach")
> Suggested-by: Péter Ujfalusi" <peter.ujfalusi@linux.intel.com>
> Signed-off-by: Tavian Barnes <tavianator@tavianator.com>
> ---
> v4: Copy the whole array, including the sentinel.
> 
> v3: Copy the whole machine struct instead so we can safely modify it
>     (instead of storing the name in pdata->tplg_filename, breaking other
>     fixups).  The problem with v2 was pointed out by Bard Liao, with the
>     alternative fix suggested by Péter Ujfalusi.
> 
> v2: Typo fix.
> 
>  sound/soc/sof/intel/hda.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/sound/soc/sof/intel/hda.c b/sound/soc/sof/intel/hda.c
> index b34e5fdf10f1..13ecb9473eb6 100644
> --- a/sound/soc/sof/intel/hda.c
> +++ b/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 */,

I would prefer the comment after the comma.
and I just noticed that my suggestion had it wrong as well, sorry.

With that you can add my:
Acked-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>

> +					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);

-- 
Péter