linux-kernel - [PATCH v3] ASoC: SOF: Intel: hda: Fix UAF when reloading module

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Message-ID: <fb47a18bdea9e9f86d6fccf1d881434cda3cd5f0.1746627007.git.tavianator@tavianator.com>
Date: Wed,  7 May 2025 11:10:24 -0400
From: Tavian Barnes <tavianator@...ianator.com>
To: linux-sound@...r.kernel.org
Cc: Tavian Barnes <tavianator@...ianator.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
	Bard Liao <yung-chuan.liao@...ux.intel.com>,
	Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
	Daniel Baluta <daniel.baluta@....com>,
	Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
	Pierre-Louis Bossart <pierre-louis.bossart@...ux.dev>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>,
	Peter Zijlstra <peterz@...radead.org>,
	sound-open-firmware@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3] 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-#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 machine with devm_kmemdup() before we modify it.

Fixes: 5458411d7594 ("ASoC: SOF: Intel: hda: refactoring topology name fixup for HDA mach")
Suggested-by: Péter Ujfalusi" <peter.ujfalusi@...ux.intel.com>
Signed-off-by: Tavian Barnes <tavianator@...ianator.com>
---
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.

 sound/soc/sof/intel/hda.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sound/soc/sof/intel/hda.c b/sound/soc/sof/intel/hda.c
index b34e5fdf10f1..cbf96b342005 100644
--- a/sound/soc/sof/intel/hda.c
+++ b/sound/soc/sof/intel/hda.c
@@ -1049,7 +1049,13 @@ 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 copy so we can modify it below */
+			hda_mach = devm_kmemdup(sdev->dev,
+						snd_soc_acpi_intel_hda_machines,
+						sizeof(*hda_mach),
+						GFP_KERNEL);
+			if (!hda_mach)
+				return;
 
 			dev_info(bus->dev, "using HDA machine driver %s now\n",
 				 hda_mach->drv_name);
-- 
2.49.0