[PATCH 6.19 223/781] ALSA: usb-audio: Relax __free() variable declarations

Greg Kroah-Hartman
2026-02-25T01:30:58Z

From: Takashi Iwai <tiwai@suse.de>

[ Upstream commit 03f705b9ca58b91c6dffe64875ea3d9a38cad9b5 ]

We used to have a variable declaration with __free() initialized with
NULL. This was to keep the old coding style rule, but recently it's
relaxed and rather recommends to follow the new rule to declare in
place of use for __free() -- which avoids potential deadlocks or UAFs
with nested cleanups.

Although the current code has no bug, per se, let's follow the new
standard and move the declaration to the place of assignment (or
directly assign the allocated result) instead of NULL initializations.

Note that there are still a few remaining __free(kfree) with NULL
initializations; they are because of the code complexity (the data
size calculation).

Fixes: 43d4940c944c ("ALSA: usb: scarlett2: Clean ups with guard() and __free()")
Fixes: 46757a3e7d50 ("ALSA: FCP: Add Focusrite Control Protocol driver")
Fixes: f7d306b47a24 ("ALSA: usb-audio: Fix a DMA to stack memory bug")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20251216140634.171890-12-tiwai@suse.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/usb/fcp.c | 36 ++++++++++++++++++------------------
sound/usb/mixer_scarlett2.c | 21 ++++++++++-----------
sound/usb/quirks.c | 13 ++++++-------
3 files changed, 34 insertions(+), 36 deletions(-)

diff --git a/sound/usb/fcp.c b/sound/usb/fcp.c
index 11e9a96b46ffe..1f4595d1e217f 100644
--- a/sound/usb/fcp.c
+++ b/sound/usb/fcp.c
@@ -182,10 +182,6 @@ static int fcp_usb(struct usb_mixer_interface *mixer, u32 opcode,
{
struct fcp_data *private = mixer->private_data;
struct usb_device *dev = mixer->chip->dev;
- struct fcp_usb_packet *req __free(kfree) = NULL;
- struct fcp_usb_packet *resp __free(kfree) = NULL;
- size_t req_buf_size = struct_size(req, data, req_size);
- size_t resp_buf_size = struct_size(resp, data, resp_size);
int retries = 0;
const int max_retries = 5;
int err;
@@ -193,10 +189,14 @@ static int fcp_usb(struct usb_mixer_interface *mixer, u32 opcode,
if (!mixer->urb)
return -ENODEV;

+ struct fcp_usb_packet *req __free(kfree) = NULL;
+ size_t req_buf_size = struct_size(req, data, req_size);
req = kmalloc(req_buf_size, GFP_KERNEL);
if (!req)
return -ENOMEM;

+ struct fcp_usb_packet *resp __free(kfree) = NULL;
+ size_t resp_buf_size = struct_size(resp, data, resp_size);
resp = kmalloc(resp_buf_size, GFP_KERNEL);
if (!resp)
return -ENOMEM;
@@ -300,16 +300,17 @@ static int fcp_usb(struct usb_mixer_interface *mixer, u32 opcode,
static int fcp_reinit(struct usb_mixer_interface *mixer)
{
struct fcp_data *private = mixer->private_data;
- void *step0_resp __free(kfree) = NULL;
- void *step2_resp __free(kfree) = NULL;

if (mixer->urb)
return 0;

- step0_resp = kmalloc(private->step0_resp_size, GFP_KERNEL);
+ void *step0_resp __free(kfree) =
+ kmalloc(private->step0_resp_size, GFP_KERNEL);
if (!step0_resp)
return -ENOMEM;
- step2_resp = kmalloc(private->step2_resp_size, GFP_KERNEL);
+
+ void *step2_resp __free(kfree) =
+ kmalloc(private->step2_resp_size, GFP_KERNEL);
if (!step2_resp)
return -ENOMEM;

@@ -464,7 +465,6 @@ static int fcp_ioctl_init(struct usb_mixer_interface *mixer,
struct fcp_init init;
struct usb_device *dev = mixer->chip->dev;
struct fcp_data *private = mixer->private_data;
- void *resp __free(kfree) = NULL;
void *step2_resp;
int err, buf_size;

@@ -485,7 +485,8 @@ static int fcp_ioctl_init(struct usb_mixer_interface *mixer,
/* Allocate response buffer */
buf_size = init.step0_resp_size + init.step2_resp_size;

- resp = kmalloc(buf_size, GFP_KERNEL);
+ void *resp __free(kfree) =
+ kmalloc(buf_size, GFP_KERNEL);
if (!resp)
return -ENOMEM;

@@ -619,7 +620,6 @@ static int fcp_ioctl_set_meter_map(struct usb_mixer_interface *mixer,
{
struct fcp_meter_map map;
struct fcp_data *private = mixer->private_data;
- s16 *tmp_map __free(kfree) = NULL;
int err;

if (copy_from_user(&map, arg, sizeof(map)))
@@ -641,7 +641,8 @@ static int fcp_ioctl_set_meter_map(struct usb_mixer_interface *mixer,
return -EINVAL;

/* Allocate and copy the map data */
- tmp_map = memdup_array_user(arg->map, map.map_size, sizeof(s16));
+ s16 *tmp_map __free(kfree) =
+ memdup_array_user(arg->map, map.map_size, sizeof(s16));
if (IS_ERR(tmp_map))
return PTR_ERR(tmp_map);

@@ -651,17 +652,16 @@ static int fcp_ioctl_set_meter_map(struct usb_mixer_interface *mixer,

/* If the control doesn't exist, create it */
if (!private->meter_ctl) {
- s16 *new_map __free(kfree) = NULL;
- __le32 *meter_levels __free(kfree) = NULL;
-
/* Allocate buffer for the map */
- new_map = kmalloc_array(map.map_size, sizeof(s16), GFP_KERNEL);
+ s16 *new_map __free(kfree) =
+ kmalloc_array(map.map_size, sizeof(s16), GFP_KERNEL);
if (!new_map)
return -ENOMEM;

/* Allocate buffer for reading meter levels */
- meter_levels = kmalloc_array(map.meter_slots, sizeof(__le32),
- GFP_KERNEL);
+ __le32 *meter_levels __free(kfree) =
+ kmalloc_array(map.meter_slots, sizeof(__le32),
+ GFP_KERNEL);
if (!meter_levels)
return -ENOMEM;

diff --git a/sound/usb/mixer_scarlett2.c b/sound/usb/mixer_scarlett2.c
index bef8c9e544dd3..88b7e42d159e0 100644
--- a/sound/usb/mixer_scarlett2.c
+++ b/sound/usb/mixer_scarlett2.c
@@ -2377,18 +2377,18 @@ static int scarlett2_usb(
{
struct scarlett2_data *private = mixer->private_data;
struct usb_device *dev = mixer->chip->dev;
- struct scarlett2_usb_packet *req __free(kfree) = NULL;
- struct scarlett2_usb_packet *resp __free(kfree) = NULL;
- size_t req_buf_size = struct_size(req, data, req_size);
- size_t resp_buf_size = struct_size(resp, data, resp_size);
int retries = 0;
const int max_retries = 5;
int err;

+ struct scarlett2_usb_packet *req __free(kfree) = NULL;
+ size_t req_buf_size = struct_size(req, data, req_size);
req = kmalloc(req_buf_size, GFP_KERNEL);
if (!req)
return -ENOMEM;

+ struct scarlett2_usb_packet *resp __free(kfree) = NULL;
+ size_t resp_buf_size = struct_size(resp, data, resp_size);
resp = kmalloc(resp_buf_size, GFP_KERNEL);
if (!resp)
return -ENOMEM;
@@ -3919,9 +3919,9 @@ static int scarlett2_input_select_ctl_info(
struct scarlett2_data *private = mixer->private_data;
int inputs = private->info->gain_input_count;
int i, err;
- char **values __free(kfree) = NULL;
+ char **values __free(kfree) =
+ kcalloc(inputs, sizeof(char *), GFP_KERNEL);

- values = kcalloc(inputs, sizeof(char *), GFP_KERNEL);
if (!values)
return -ENOMEM;

@@ -9083,8 +9083,6 @@ static long scarlett2_hwdep_read(struct snd_hwdep *hw,
__le32 len;
} __packed req;

- u8 *resp __free(kfree) = NULL;
-
/* Flash segment must first be selected */
if (private->flash_write_state != SCARLETT2_FLASH_WRITE_STATE_SELECTED)
return -EINVAL;
@@ -9122,7 +9120,8 @@ static long scarlett2_hwdep_read(struct snd_hwdep *hw,
req.offset = cpu_to_le32(*offset);
req.len = cpu_to_le32(count);

- resp = kzalloc(count, GFP_KERNEL);
+ u8 *resp __free(kfree) =
+ kzalloc(count, GFP_KERNEL);
if (!resp)
return -ENOMEM;

@@ -9267,7 +9266,6 @@ static ssize_t scarlett2_devmap_read(
loff_t pos)
{
struct usb_mixer_interface *mixer = entry->private_data;
- u8 *resp_buf __free(kfree) = NULL;
const size_t block_size = SCARLETT2_DEVMAP_BLOCK_SIZE;
size_t copied = 0;

@@ -9277,7 +9275,8 @@ static ssize_t scarlett2_devmap_read(
if (pos + count > entry->size)
count = entry->size - pos;

- resp_buf = kmalloc(block_size, GFP_KERNEL);
+ u8 *resp_buf __free(kfree) =
+ kmalloc(block_size, GFP_KERNEL);
if (!resp_buf)
return -ENOMEM;

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 2d9f28558874c..4f9d19bf1ccac 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -555,7 +555,6 @@ int snd_usb_create_quirk(struct snd_usb_audio *chip,
static int snd_usb_extigy_boot_quirk(struct usb_device *dev, struct usb_interface *intf)
{
struct usb_host_config *config = dev->actconfig;
- struct usb_device_descriptor *new_device_descriptor __free(kfree) = NULL;
int err;

if (le16_to_cpu(get_cfg_desc(config)->wTotalLength) == EXTIGY_FIRMWARE_SIZE_OLD ||
@@ -566,8 +565,8 @@ static int snd_usb_extigy_boot_quirk(struct usb_device *dev, struct usb_interfac
0x10, 0x43, 0x0001, 0x000a, NULL, 0);
if (err < 0)
dev_dbg(&dev->dev, "error sending boot message: %d\n", err);
-
- new_device_descriptor = kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
+ struct usb_device_descriptor *new_device_descriptor __free(kfree) =
+ kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
if (!new_device_descriptor)
return -ENOMEM;
err = usb_get_descriptor(dev, USB_DT_DEVICE, 0,
@@ -910,7 +909,6 @@ static void mbox2_setup_48_24_magic(struct usb_device *dev)
static int snd_usb_mbox2_boot_quirk(struct usb_device *dev)
{
struct usb_host_config *config = dev->actconfig;
- struct usb_device_descriptor *new_device_descriptor __free(kfree) = NULL;
int err;
u8 bootresponse[0x12];
int fwsize;
@@ -945,7 +943,8 @@ static int snd_usb_mbox2_boot_quirk(struct usb_device *dev)

dev_dbg(&dev->dev, "device initialised!\n");

- new_device_descriptor = kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
+ struct usb_device_descriptor *new_device_descriptor __free(kfree) =
+ kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
if (!new_device_descriptor)
return -ENOMEM;

@@ -1267,7 +1266,6 @@ static void mbox3_setup_defaults(struct usb_device *dev)
static int snd_usb_mbox3_boot_quirk(struct usb_device *dev)
{
struct usb_host_config *config = dev->actconfig;
- struct usb_device_descriptor *new_device_descriptor __free(kfree) = NULL;
int err;
int descriptor_size;

@@ -1280,7 +1278,8 @@ static int snd_usb_mbox3_boot_quirk(struct usb_device *dev)

dev_dbg(&dev->dev, "MBOX3: device initialised!\n");

- new_device_descriptor = kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
+ struct usb_device_descriptor *new_device_descriptor __free(kfree) =
+ kmalloc(sizeof(*new_device_descriptor), GFP_KERNEL);
if (!new_device_descriptor)
return -ENOMEM;

--
2.51.0